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Insects
Volume 11
Issue 2
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Insects, Volume 11, Issue 2 (February 2020) – 73 articles

Cover Story (view full-size image): In the UK, severe infestations by Plutella xylostella occur sporadically and are due mainly to the immigration of moths. The aim of this study was to improve warnings to growers about moth influxes. Populations were monitored using pheromone traps, by counting immature stages on plants and by accessing citizen science data. Analysis of historical weather data showed that the immediate sources of immigrant moths were countries in the western part of continental Europe. A network of pheromone traps, each containing a small camera sending images to a website, provided accessible and timely information, but the system tested did not catch many moths. In another approach, sightings by citizen scientists were summarised on a web page. These were accessed regularly by growers and, at present, this approach appears to be the most effective way of providing timely warnings. View this paper
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16 pages, 6519 KiB  
Article
Nest Turrets of Acromyrmex Grass-Cutting Ants: Micromorphology Reveals Building Techniques and Construction Dynamics
by Marcela I. Cosarinsky, Daniela Römer and Flavio Roces
Insects 2020, 11(2), 140; https://doi.org/10.3390/insects11020140 - 24 Feb 2020
Cited by 7 | Viewed by 4834
Abstract
Acromyrmex fracticornis grass-cutting ants construct conspicuous chimney-shaped nest turrets made of intermeshed grass fragments. We asked whether turrets are constructed by merely piling up nearby materials around the entrance, or whether ants incorporate different materials as the turret develops. By removing the original [...] Read more.
Acromyrmex fracticornis grass-cutting ants construct conspicuous chimney-shaped nest turrets made of intermeshed grass fragments. We asked whether turrets are constructed by merely piling up nearby materials around the entrance, or whether ants incorporate different materials as the turret develops. By removing the original nest turrets and following their rebuilding process over three consecutive days, age-dependent changes in wall morphology and inner lining fabrics were characterized. Micromorphological descriptions based on thin sections of turret walls revealed the building behaviors involved. Ants started by collecting nearby twigs and dry grass fragments that are piled up around the nest entrance. Several large fragments held the structure like beams. As a net-like structure grew, soil pellets were placed in between the intermeshed plant fragments from the turret base to the top, reinforcing the structure. Concomitantly, the turret inner wall was lined with soil pellets, starting from the base. Therefore, the consolidation of the turret occurred both over time and from its base upwards. It is argued that nest turrets do not simply arise by the arbitrary deposition of nearby materials, and that workers selectively incorporate large materials at the beginning, and respond to the developing structure by reinforcing the intermeshed plant fragments over time. Full article
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14 pages, 10623 KiB  
Article
Transcriptomic Analysis of the Brown Planthopper, Nilaparvata lugens, at Different Stages after Metarhizium anisopliae Challenge
by Yifan Peng, Jifeng Tang and Jiaqin Xie
Insects 2020, 11(2), 139; https://doi.org/10.3390/insects11020139 - 24 Feb 2020
Cited by 6 | Viewed by 3220
Abstract
Nilaparvata lugens is one of the major pests of rice and results in substantial yield loss every year. Our previous study found that the entomopathogenic fungus Metarhizium anisopliae showed effective potential for controlling this pest. However, the mechanisms underlying M. anisopliae infection of [...] Read more.
Nilaparvata lugens is one of the major pests of rice and results in substantial yield loss every year. Our previous study found that the entomopathogenic fungus Metarhizium anisopliae showed effective potential for controlling this pest. However, the mechanisms underlying M. anisopliae infection of N. lugens are not well known. In the present study, we further examined the transcriptome of N. lugens at 4 h, 8 h, 16 h, and 24 h after M. anisopliae infection by Illumina deep sequencing. In total, 174.17 Gb of data was collected after sequencing, from which 23,398 unigenes were annotated by various databases, including 3694 newly annotated genes. The results showed that there were 246 vs 75, 275 vs 586, 378 vs 1055, and 638 vs 182 up- and downregulated differentially expressed genes (DEGs) at 4 h, 8 h, 16 h, and 24 h after M. anisopliae infection, respectively. The biological functions and associated metabolic processes of these genes were determined with the Clusters of Orthologous Groups (COG), Gene Ontology (GO), and Kyoto Encyclopedia of Genes and Genomes (KEGG) databases. The DEGs data were verified using RT-qPCR. These results indicated that the DEGs during the initial fungal infection appropriately reflected the time course of the response to the fungal infection. Taken together, the results of this study provide new insights into the molecular mechanisms underlying the insect host response to fungal infection, especially during the initial stage of infection, and may improve the potential control strategies for N. lugens. Full article
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13 pages, 2718 KiB  
Article
Male-Produced (−)-δ-Heptalactone, Pheromone of Fruit Fly Rhagoletis batava (Diptera: Tephritidae), a Sea Buckthorn Berries Pest
by Vincas Būda, Laima Blažytė-Čereškienė, Sandra Radžiutė, Violeta Apšegaitė, Patrick Stamm, Stefan Schulz, Dominykas Aleknavičius and Raimondas Mozūraitis
Insects 2020, 11(2), 138; https://doi.org/10.3390/insects11020138 - 23 Feb 2020
Cited by 8 | Viewed by 4023
Abstract
The plantation area of sea buckthorn (Hippophae rhamnoides L.) is expanding in many European countries due to increasing demand for berries, thus creating suitable conditions for the rapid expansion of the fruit fly Rhagoletis batava, a pest of economic importance. To [...] Read more.
The plantation area of sea buckthorn (Hippophae rhamnoides L.) is expanding in many European countries due to increasing demand for berries, thus creating suitable conditions for the rapid expansion of the fruit fly Rhagoletis batava, a pest of economic importance. To decrease insecticide use, effective means for pest population monitoring are required, including the use of pheromones. Male fruit flies emit (-)-δ-heptalactone as revealed by gas chromatography-mass spectrometry analyses of samples obtained using headspace methods. The two enantiomers of δ-heptalactone were synthesized using enantioselective synthesis. A gas chromatography-electroantennographic detection analysis of both stereoisomers revealed that only (-)-δ-heptalactone elicited electrophysiological responses, whereas no signal was registered to (+)-δ-heptalactone in fruit flies of either sex. In the field assay, traps baited with (-)-δ-heptalactone caught significantly more fruit flies compared with the unbaited traps. Our results are the first to demonstrate the efficacy of (-)-δ-heptalactone as a bait for trapping R. batava. As a behaviorally attractive compound to R. batava fruit flies of both sexes, (-)-δ-heptalactone is attributed to aggregation pheromones. This is the first report of an aggregation pheromone within the genus Rhagoletis. Full article
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26 pages, 6230 KiB  
Article
Comparative Antennal Morphology of Agriotes (Coleoptera: Elateridae), with Special Reference to the Typology and Possible Functions of Sensilla
by Michel J. Faucheux, Tamás Németh and Robin Kundrata
Insects 2020, 11(2), 137; https://doi.org/10.3390/insects11020137 - 21 Feb 2020
Cited by 15 | Viewed by 5129
Abstract
Species of the click-beetle genus Agriotes Eschscholtz are economically important crop pests distributed mainly in the Northern Hemisphere. They can inflict considerable damage on various field crops. Therefore, the detection, monitoring, and control of Agriotes include the adult trapping using species-specific sex pheromones, [...] Read more.
Species of the click-beetle genus Agriotes Eschscholtz are economically important crop pests distributed mainly in the Northern Hemisphere. They can inflict considerable damage on various field crops. Therefore, the detection, monitoring, and control of Agriotes include the adult trapping using species-specific sex pheromones, which is a critical component of pest research. To obtain a better understanding of the detailed antennal morphology as background information for subsequent chemical ecology research, we conducted a scanning electron microscopy study of the antennal sensilla of both sexes in 10 European Agriotes species. We identified 16 different sensilla in Agriotes, belonging to six main types: sensilla chaetica (subtypes C1 and C2), sensilla trichodea, sensilla basiconica (subtypes B1–B9), dome-shaped sensilla (subtypes D1 and D2), sensilla campaniformia, and Böhm sensilla. We discuss their possible functions and compare the sensilla of Agriotes with those of other Elateridae in order to consolidate the sensillum nomenclature in this family. Additionally, our study reveals the remarkable interspecific variability in sensillar equipment of Agriotes and identifies several characters of potential importance for future use in systematic studies. The present study provides a strong preliminary framework for subsequent research on the antennal morphology of this crop pest on a wider scale. Full article
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18 pages, 2850 KiB  
Article
Low Host Specialization in the Cuckoo Wasp, Parnopes grandior, Weakens Chemical Mimicry but Does Not Lead to Local Adaption
by Carlo Polidori, Yolanda Ballesteros, Mareike Wurdack, Josep Daniel Asís, José Tormos, Laura Baños-Picón and Thomas Schmitt
Insects 2020, 11(2), 136; https://doi.org/10.3390/insects11020136 - 20 Feb 2020
Cited by 5 | Viewed by 3661
Abstract
Insect brood parasites have evolved a variety of strategies to avoid being detected by their hosts. Few previous studies on cuckoo wasps (Hymenoptera: Chrysididae), which are natural enemies of solitary wasps and bees, have shown that chemical mimicry, i.e., the biosynthesis of cuticular [...] Read more.
Insect brood parasites have evolved a variety of strategies to avoid being detected by their hosts. Few previous studies on cuckoo wasps (Hymenoptera: Chrysididae), which are natural enemies of solitary wasps and bees, have shown that chemical mimicry, i.e., the biosynthesis of cuticular hydrocarbons (CHC) that match the host profile, evolved in several species. However, mimicry was not detected in all investigated host-parasite pairs. The effect of host range as a second factor that may play a role in evolution of mimicry has been neglected, since all previous studies were carried out on host specialists and at nesting sites where only one host species occurred. Here we studied the cuckoo wasp Parnopes grandior, which attacks many digger wasp species of the genus Bembix (Hymenoptera: Crabronidae). Given its weak host specialization, P. grandior may either locally adapt by increasing mimicry precision to only one of the sympatric hosts or it may evolve chemical insignificance by reducing the CHC profile complexity and/or CHCs amounts. At a study site harbouring three host species, we found evidence for a weak but appreciable chemical deception strategy in P. grandior. Indeed, the CHC profile of P. grandior was more similar to all sympatric Bembix species than to a non-host wasp species belonging to the same tribe as Bembix. Furthermore, P. grandior CHC profile was equally distant to all the hosts’ CHC profiles, thus not pointing towards local adaptation of the CHC profile to one of the hosts’ profile. We conducted behavioural assays suggesting that such weak mimicry is sufficient to reduce host aggression, even in absence of an insignificance strategy, which was not detected. Hence, we finally concluded that host range may indeed play a role in shaping the level of chemical mimicry in cuckoo wasps. Full article
(This article belongs to the Special Issue Semiochemicals and Insect Behavior)
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15 pages, 1120 KiB  
Article
The ABCB Multidrug Resistance Proteins Do Not Contribute to Ivermectin Detoxification in the Colorado Potato Beetle, Leptinotarsa decemlineata (Say)
by Grant Favell, Jeremy N. McNeil and Cam Donly
Insects 2020, 11(2), 135; https://doi.org/10.3390/insects11020135 - 20 Feb 2020
Cited by 7 | Viewed by 3304
Abstract
The Colorado potato beetle, Leptinotarsa decemlineata (Say), is a significant agricultural pest that has developed resistance to many insecticides that are used to control it. Investigating the mechanisms of insecticide detoxification in this pest is important for ensuring its continued control, since they [...] Read more.
The Colorado potato beetle, Leptinotarsa decemlineata (Say), is a significant agricultural pest that has developed resistance to many insecticides that are used to control it. Investigating the mechanisms of insecticide detoxification in this pest is important for ensuring its continued control, since they may be contributors to such resistance. Multidrug resistance (MDR) genes that code for the ABCB transmembrane efflux transporters are one potential source of insecticide detoxification activity that have not been thoroughly examined in L. decemlineata. In this study, we annotated the ABCB genes found in the L. decemlineata genome and then characterized the expression profiles across midgut, nerve, and Malpighian tubule tissues of the three full transporters identified. To investigate if these genes are involved in defense against the macrocyclic lactone insecticide ivermectin in this insect, each gene was silenced using RNA interference or MDR protein activity was inhibited using a chemical inhibitor, verapamil, before challenging the insects with a dose of ivermectin. Survival of the insects did not significantly change due to gene silencing or protein inhibition, suggesting that MDR transporters do not significantly contribute to defense against ivermectin in L. decemlineata. Full article
(This article belongs to the Special Issue Insecticide Resistance: The Genetic Basis and Underlying Mechanisms in Potato Pests)
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19 pages, 2250 KiB  
Case Report
First Insight into Microbiome Profiles of Myrmecophilous Beetles and Their Host, Red Wood Ant Formica polyctena (Hymenoptera: Formicidae)—A Case Study
by Agnieszka Kaczmarczyk-Ziemba, Mirosław Zagaja, Grzegorz K. Wagner, Ewa Pietrykowska-Tudruj and Bernard Staniec
Insects 2020, 11(2), 134; https://doi.org/10.3390/insects11020134 - 19 Feb 2020
Cited by 8 | Viewed by 4473
Abstract
Formica polyctena belongs to the red wood ant species group. Its nests provide a stable, food rich, and temperature and humidity controlled environment, utilized by a wide range of species, called myrmecophiles. Here, we used the high-throughput sequencing of the 16S rRNA gene [...] Read more.
Formica polyctena belongs to the red wood ant species group. Its nests provide a stable, food rich, and temperature and humidity controlled environment, utilized by a wide range of species, called myrmecophiles. Here, we used the high-throughput sequencing of the 16S rRNA gene on the Illumina platform for identification of the microbiome profiles of six selected myrmecophilous beetles (Dendrophilus pygmaeus, Leptacinus formicetorum, Monotoma angusticollis, Myrmechixenus subterraneus, Ptenidium formicetorum and Thiasophila angulata) and their host F. polyctena. Analyzed bacterial communities consisted of a total of 23 phyla, among which Proteobacteria, Actinobacteria, and Firmicutes were the most abundant. Two known endosymbionts—Wolbachia and Rickettsia—were found in the analyzed microbiome profiles and Wolbachia was dominant in bacterial communities associated with F. polyctena, M. subterraneus, L. formicetorum and P. formicetorum (>90% of reads). In turn, M. angusticollis was co-infected with both Wolbachia and Rickettsia, while in the microbiome of T. angulata, the dominance of Rickettsia has been observed. The relationships among the microbiome profiles were complex, and no relative abundance pattern common to all myrmecophilous beetles tested was observed. However, some subtle, species-specific patterns have been observed for bacterial communities associated with D. pygmaeus, M. angusticollis, and T. angulata. Full article
(This article belongs to the Special Issue Ants as Partners and Hosts)
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13 pages, 1506 KiB  
Article
Synergistic Toxicity Interactions between Plant Essential Oil Components against the Common Bed Bug (Cimex lectularius L.)
by Sudip Gaire, Michael E. Scharf and Ameya D. Gondhalekar
Insects 2020, 11(2), 133; https://doi.org/10.3390/insects11020133 - 19 Feb 2020
Cited by 32 | Viewed by 5906
Abstract
Management of the common bed bug (Cimex lectularius L.) necessitates the use of multiple control techniques. In addition to synthetic pesticides and mechanical interventions, plant-derived essential oils represent one of the control options. Mixtures of two or more essential oil components (monoterpenoids) [...] Read more.
Management of the common bed bug (Cimex lectularius L.) necessitates the use of multiple control techniques. In addition to synthetic pesticides and mechanical interventions, plant-derived essential oils represent one of the control options. Mixtures of two or more essential oil components (monoterpenoids) exhibit synergistic toxicity effects against insects due to increased cuticular penetration. Monoterpenoids, such as carvacrol, eugenol and thymol, are neurologically active and inhibit the nerve firing activity of C. lectularius. However, the effects of mixtures of these monoterpenoids on their toxicity and neuroinhibitory potential against C. lectularius are not known. In this study, the toxicity levels of a tertiary mixture of carvacrol, eugenol and thymol (1:1:1 ratio) and a binary mixture of synthetic insecticides, bifenthrin and imidacloprid (1:1 ratio) were evaluated against C. lectularius through topical bioassays and electrophysiology experiments. Both a mixture of monoterpenoids and the mixture of synthetic insecticides exhibited synergistic effects in topical bioassays. In electrophysiology experiments, the monoterpenoid mixture led to greater neuroinhibitory effects, whereas a mixture of synthetic insecticides caused higher neuroexcitatory effects in comparison to single compounds. This study shows evidence for neurological mechanisms of synergistic interactions between monoterpenoids and provides information regarding the utilization of natural compound mixtures for C. lectularius management. Full article
(This article belongs to the Special Issue Biology and Management of Bed Bugs)
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14 pages, 1706 KiB  
Article
Pollen Protein: Lipid Macronutrient Ratios May Guide Broad Patterns of Bee Species Floral Preferences
by Anthony D. Vaudo, John F. Tooker, Harland M. Patch, David J. Biddinger, Michael Coccia, Makaylee K. Crone, Mark Fiely, Jacob S. Francis, Heather M. Hines, Mackenzie Hodges, Stephanie W. Jackson, Denis Michez, Junpeng Mu, Laura Russo, Maliheh Safari, Erin D. Treanore, Maryse Vanderplanck, Eric Yip, Anne S. Leonard and Christina M. Grozinger
Insects 2020, 11(2), 132; https://doi.org/10.3390/insects11020132 - 18 Feb 2020
Cited by 152 | Viewed by 16468
Abstract
Pollinator nutritional ecology provides insights into plant–pollinator interactions, coevolution, and the restoration of declining pollinator populations. Bees obtain their protein and lipid nutrient intake from pollen, which is essential for larval growth and development as well as adult health and reproduction. Our previous [...] Read more.
Pollinator nutritional ecology provides insights into plant–pollinator interactions, coevolution, and the restoration of declining pollinator populations. Bees obtain their protein and lipid nutrient intake from pollen, which is essential for larval growth and development as well as adult health and reproduction. Our previous research revealed that pollen protein to lipid ratios (P:L) shape bumble bee foraging preferences among pollen host-plant species, and these preferred ratios link to bumble bee colony health and fitness. Yet, we are still in the early stages of integrating data on P:L ratios across plant and bee species. Here, using a standard laboratory protocol, we present over 80 plant species’ protein and lipid concentrations and P:L values, and we evaluate the P:L ratios of pollen collected by three bee species. We discuss the general phylogenetic, phenotypic, behavioral, and ecological trends observed in these P:L ratios that may drive plant–pollinator interactions; we also present future research questions to further strengthen the field of pollination nutritional ecology. This dataset provides a foundation for researchers studying the nutritional drivers of plant–pollinator interactions as well as for stakeholders developing planting schemes to best support pollinators. Full article
(This article belongs to the Special Issue Mechanisms of Nutritional Resource Exploitation by Insects)
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20 pages, 2351 KiB  
Article
Agar and Carrageenan as Cost-Effective Gelling Agents in Yeast-Reduced Artificial Diets for Mass-Rearing Fruit Flies and Their Parasitoids
by Carlos Pascacio-Villafán, Larissa Guillén and Martín Aluja
Insects 2020, 11(2), 131; https://doi.org/10.3390/insects11020131 - 18 Feb 2020
Cited by 18 | Viewed by 4922
Abstract
The development of cost-effective diets for mass-rearing fruit flies (Diptera: Tephritidae) and their parasitoids in pest control programs based on the Sterile Insect Technique is a high priority worldwide. To this end, we tested carrageenan, agar, gelatin and two types of pregelatinized corn [...] Read more.
The development of cost-effective diets for mass-rearing fruit flies (Diptera: Tephritidae) and their parasitoids in pest control programs based on the Sterile Insect Technique is a high priority worldwide. To this end, we tested carrageenan, agar, gelatin and two types of pregelatinized corn starches as gelling agents at varying percentages in a yeast-reduced liquid larval diet for rearing the Mexfly, Anastrepha ludens. Only diets with 0.234% (w/w) agar or 0.424% carrageenan were identified as diets with potential for mass-rearing A. ludens in terms of the number of pupae recovered from the diet, pupal weight, adult emergence, flight ability and diet cost. Comparative experiments showed that yeast-reduced agar and carrageenan gel diets produced heavier pupae and higher proportions of flying adults than the standard mass-rearing diet. The gel-agar and mass-rearing diets produced more pupae than the gel-carrageenan diet, but the latter produced more suitable larvae as hosts for rearing of Diachasmimorpha longicaudata (Hymenoptera: Braconidae) females, a widely used fruit fly biocontrol agent. Yeast-reduced agar and carrageenan gel diets could represent cost-effective fruit fly mass-rearing diets if a practical system for gel diet preparation and dispensation at fruit fly mass-rearing facilities is developed. Full article
(This article belongs to the Special Issue Sterile Insect Technique (SIT) and Its Applications)
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21 pages, 3742 KiB  
Article
Spittlebugs of Mediterranean Olive Groves: Host-Plant Exploitation throughout the Year
by Nicola Bodino, Vincenzo Cavalieri, Crescenza Dongiovanni, Matteo Alessandro Saladini, Anna Simonetto, Stefania Volani, Elisa Plazio, Giuseppe Altamura, Daniele Tauro, Gianni Gilioli and Domenico Bosco
Insects 2020, 11(2), 130; https://doi.org/10.3390/insects11020130 - 18 Feb 2020
Cited by 62 | Viewed by 5915
Abstract
Spittlebugs are the vectors of the bacterium Xylella fastidiosa Wells in Europe, the causal agent of olive dieback epidemic in Apulia, Italy. Selection and distribution of different spittlebug species on host-plants were investigated during field surveys in 2016–2018 in four olive orchards of [...] Read more.
Spittlebugs are the vectors of the bacterium Xylella fastidiosa Wells in Europe, the causal agent of olive dieback epidemic in Apulia, Italy. Selection and distribution of different spittlebug species on host-plants were investigated during field surveys in 2016–2018 in four olive orchards of Apulia and Liguria Regions of Italy. The nymphal population in the herbaceous cover was estimated using quadrat samplings. Adults were collected by sweeping net on three different vegetational components: herbaceous cover, olive canopy, and wild woody plants. Three species of spittlebugs were collected: Philaenus spumarius L., Neophilaenus campestris (Fallén), and Aphrophora alni (L.) (Hemiptera: Aphrophoridae). Philaenus spumarius was the predominant species both in Apulia and Liguria olive groves. Nymphal stages are highly polyphagous, selecting preferentially Asteraceae Fabaceae plant families, in particular some genera, e.g., Picris, Crepis, Sonchus, Bellis, Cichorium, and Medicago. Host-plant preference of nymphs varies according to the Region and through time and nymphal instar. In the monitored sites, adults peak on olive trees earlier in Apulia (i.e., during inflorescence emergence) than in Liguria (i.e., during flowering and beginning of fruit development). Principal alternative woody hosts are Quercus spp. and Pistacia spp. Knowledge concerning plant selection and ecological traits of spittlebugs in different Mediterranean olive production areas is needed to design effective and precise control strategies against X. fastidiosa vectors in olive groves, such as ground cover modifications to reduce populations of spittlebug vectors. Full article
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21 pages, 3641 KiB  
Article
New Tools for Conservation Biological Control: Testing Ant-Attracting Artificial Nectaries to Employ Ants as Plant Defenders
by Enrico Schifani, Cristina Castracani, Daniele Giannetti, Fiorenza Augusta Spotti, Roberto Reggiani, Stefano Leonardi, Alessandra Mori and Donato Antonio Grasso
Insects 2020, 11(2), 129; https://doi.org/10.3390/insects11020129 - 17 Feb 2020
Cited by 31 | Viewed by 4993
Abstract
Knowledge of the role of ants in many agroecosystems is relatively scarce, and in temperate regions the possibility to exploit ants as biocontrol agents for crop protection is still largely unexplored. Drawing inspiration from mutualistic ant–plant relationships mediated by extrafloral nectaries (EFNs), we [...] Read more.
Knowledge of the role of ants in many agroecosystems is relatively scarce, and in temperate regions the possibility to exploit ants as biocontrol agents for crop protection is still largely unexplored. Drawing inspiration from mutualistic ant–plant relationships mediated by extrafloral nectaries (EFNs), we tested the use of artificial nectaries (ANs) in order to increase ant activity on pear trees and to evaluate the effects on the arthropods, plant health and fruit production. While EFNs secrete a complex solution mainly composed of sugars and amino acids, ANs were filled with water and sucrose only. The results suggest that ANs can be used as manipulative instruments to increase ant activity over long periods of time. High ant activity was significantly linked to lower incidence of the pathogen fungus Venturia pyrina (pear scab) on pear leaves, and of the presence of Cydia pomonella (codling moth) caterpillars on pear fruit production. These results further encourage exploring underrated possibilities in the development of new tools for conservation biological control (CBC). Full article
(This article belongs to the Special Issue IPM and Pesticide Alternatives for Orchards)
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7 pages, 242 KiB  
Communication
The Mosquito Larvicidal Activity of Essential Oils from Cymbopogon and Eucalyptus Species in Vietnam
by Ho Dung Manh, Do Thi Hue, Nguyen Thi Thanh Hieu, Doan Thi Thanh Tuyen and Ong Thi Tuyet
Insects 2020, 11(2), 128; https://doi.org/10.3390/insects11020128 - 17 Feb 2020
Cited by 40 | Viewed by 7550
Abstract
The larvicidal activity of essential oils (EOs) extracted from Cymbopogon citratus, Cymbopogon winterianus, Eucalyptus citriodora, and Eucalyptus camaldulensis aromatic plants grown in Vietnam was evaluated on Aedes aegypti larvae. The EOs were hydro-distilled in a Clevenger-type apparatus. The EOs were analyzed by [...] Read more.
The larvicidal activity of essential oils (EOs) extracted from Cymbopogon citratus, Cymbopogon winterianus, Eucalyptus citriodora, and Eucalyptus camaldulensis aromatic plants grown in Vietnam was evaluated on Aedes aegypti larvae. The EOs were hydro-distilled in a Clevenger-type apparatus. The EOs were analyzed by gas chromatography–mass spectrometry (GC–MS). The mortality rates obtained from the bioassays were used to calculate the lethal concentrations (LC50) of the EOs by the probit analysis method. These essential oils exhibited toxicity to the larvae of Aedes aegypti. Results were obtained for Cymbopogon citratus (LC50 = 120.6 ppm), Cymbopogon winterianus (LC50 = 38.8 ppm), Eucalyptus citriodora (LC50 = 104.4 ppm), and Eucalyptus camaldulensis (LC50 = 33.7 ppm). The essential oils of Eucalyptus camaldulensis and Cymbopogon winterianus were found to be the most efficient, and their respective values of LC50 were 33.7 ppm, 38.8 ppm. In conclusion, this research adds to the growing body of literature on natural larvicides from essential oils against Aedes aegypti mosquitoes. Full article
(This article belongs to the Special Issue Natural Substances against Insect Pests: Assets and Liabilities)
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12 pages, 1119 KiB  
Article
Oviposition Preference of the Cabbage Root Fly towards Some Chinese Cabbage Cultivars: A Search for Future Trap Crop Candidates
by Fabrice Lamy, Laura Bellec, Amélie Rusu-Stievenard, Pauline Clin, Claire Ricono, Diane Olivier, Solène Mauger, Denis Poinsot, Vincent Faloya, Loïc Daniel and Anne Marie Cortesero
Insects 2020, 11(2), 127; https://doi.org/10.3390/insects11020127 - 17 Feb 2020
Cited by 8 | Viewed by 3978
Abstract
The development of integrated pest management strategies becomes more and more pressing in view of potential harmful effects of synthetic pesticides on the environment and human health. A promising alternative strategy against Delia radicum is the use of trap crops. Chinese cabbage ( [...] Read more.
The development of integrated pest management strategies becomes more and more pressing in view of potential harmful effects of synthetic pesticides on the environment and human health. A promising alternative strategy against Delia radicum is the use of trap crops. Chinese cabbage (Brassica rapa subsp. pekinensis and subsp. chinensis) is a highly sensitive Brassicaceae species previously identified as a good candidate to attract the cabbage root fly away from other crops. Here, we carried out multi-choice experiments both in the laboratory and in field conditions to measure the oviposition susceptibilities of different subspecies and cultivars of Chinese cabbages as compared to a broccoli reference. We found large differences among subspecies and cultivars of the Chinese cabbage, which received three to eleven times more eggs than the broccoli reference in field conditions. In laboratory conditions, the chinensis subspecies did not receive more eggs than the broccoli reference. We conclude that D. radicum largely prefers to lay eggs on the pekinensis subspecies of Chinese cabbage compared to the chinensis subspecies or broccoli. Some pekinensis cultivars, which received over ten times more eggs than broccoli in the field, appear especially promising candidates to further develop trap crop strategies against the cabbage root fly. Full article
(This article belongs to the Collection Integrated Pest Management Strategies for Horticultural Crops)
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15 pages, 5853 KiB  
Article
Molecular Characterization and Expression Profiling of Nuclear Receptor Gene Families in Oriental Fruit Fly, Bactrocera Dorsalis (Hendel)
by Pei-Jin Yang, Er-Hu Chen, Zhong-Hao Song, Wang He, Shi-Huo Liu, Wei Dou and Jin-Jun Wang
Insects 2020, 11(2), 126; https://doi.org/10.3390/insects11020126 - 16 Feb 2020
Cited by 8 | Viewed by 3094
Abstract
The oriental fruit fly (Bactrocera dorsalis) is a pest that causes large economic losses in the fruit and vegetable industry, so its control is a major challenge. Nuclear receptors (NRs) are a superfamily of ligand-dependent transcription factors that directly combine with [...] Read more.
The oriental fruit fly (Bactrocera dorsalis) is a pest that causes large economic losses in the fruit and vegetable industry, so its control is a major challenge. Nuclear receptors (NRs) are a superfamily of ligand-dependent transcription factors that directly combine with DNA to regulate the expression of downstream target genes. NRs are closely associated with multiple physiological processes such as metabolism, reproduction, and development. Through sequence searches and analysis, we identified 21 B. dorsalis NR genes, all of which contained at least one of the two characteristic binding domains. On the basis of the conserved sequences and phylogenetic relationships, we divided the 21 NR genes into seven subfamilies. All members of the NR0 subfamily and BdHR83, which belonged to the NR2E group, lacked ligand-binding domains. The BdDSF and BdHR51, which also belonged to the NR2Egroup, and BdE78 (which belonged to the NR1E group) all lacked DNA-binding domains. The BdDSF and BdHR83 sequences were incomplete, and were not successfully amplified. Development- and tissue-specific expression profiling demonstrated that the transcript levels of the 19 NR genes varied considerably among eggs, larva, pupae, and adults, as well as among larval and adult male and female tissues. Our results will contribute to a better understanding of NR evolution and expand our knowledge of B. dorsalis physiology. Full article
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19 pages, 1505 KiB  
Article
Floral Species Richness Correlates with Changes in the Nutritional Quality of Larval Diets in a Stingless Bee
by Moritz Trinkl, Benjamin F. Kaluza, Helen Wallace, Tim A. Heard, Alexander Keller and Sara D. Leonhardt
Insects 2020, 11(2), 125; https://doi.org/10.3390/insects11020125 - 15 Feb 2020
Cited by 29 | Viewed by 6208
Abstract
Bees need food of appropriate nutritional quality to maintain their metabolic functions. They largely obtain all required nutrients from floral resources, i.e., pollen and nectar. However, the diversity, composition and nutritional quality of floral resources varies with the surrounding environment and can be [...] Read more.
Bees need food of appropriate nutritional quality to maintain their metabolic functions. They largely obtain all required nutrients from floral resources, i.e., pollen and nectar. However, the diversity, composition and nutritional quality of floral resources varies with the surrounding environment and can be strongly altered in human-impacted habitats. We investigated whether differences in plant species richness as found in the surrounding environment correlated with variation in the floral diversity and nutritional quality of larval provisions (i.e., mixtures of pollen, nectar and salivary secretions) composed by the mass-provisioning stingless bee Tetragonula carbonaria (Apidae: Meliponini). We found that the floral diversity of larval provisions increased with increasing plant species richness. The sucrose and fat (total fatty acid) content and the proportion and concentration of the omega-6 fatty acid linoleic acid decreased, whereas the proportion of the omega-3 fatty acid linolenic acid increased with increasing plant species richness. Protein (total amino acid) content and amino acid composition did not change. The protein to fat (P:F) ratio, known to affect bee foraging, increased on average by more than 40% from plantations to forests and gardens, while the omega-6:3 ratio, known to negatively affect cognitive performance, decreased with increasing plant species richness. Our results suggest that plant species richness may support T. carbonaria colonies by providing not only a continuous resource supply (as shown in a previous study), but also floral resources of high nutritional quality. Full article
(This article belongs to the Special Issue Mechanisms of Nutritional Resource Exploitation by Insects)
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18 pages, 1978 KiB  
Article
Propolis Consumption Reduces Nosema ceranae Infection of European Honey Bees (Apis mellifera)
by Alessandra Mura, Michelina Pusceddu, Panagiotis Theodorou, Alberto Angioni, Ignazio Floris, Robert J. Paxton and Alberto Satta
Insects 2020, 11(2), 124; https://doi.org/10.3390/insects11020124 - 15 Feb 2020
Cited by 38 | Viewed by 7083
Abstract
Nosema ceranae is a widespread obligate intracellular parasite of the ventriculus of many species of honey bee (Apis), including the Western honey bee Apis mellifera, in which it may lead to colony death. It can be controlled in A. mellifera [...] Read more.
Nosema ceranae is a widespread obligate intracellular parasite of the ventriculus of many species of honey bee (Apis), including the Western honey bee Apis mellifera, in which it may lead to colony death. It can be controlled in A. mellifera by feeding the antibiotic fumagillin to a colony, though this product is toxic to humans and its use has now been banned in many countries, so in beekeeping, there exists a need for alternative and safe products effective against N. ceranae. Honeybees produce propolis from resinous substances collected from plants and use it to protect their nest from parasites and pathogens; propolis is thought to decrease the microbial load of the hive. We hypothesized that propolis might also reduce N. ceranae infection of individual bees and that they might consume propolis as a form of self-medication. To test these hypotheses, we evaluated the effects of an ethanolic extract of propolis administered orally on the longevity and spore load of experimentally N. ceranae-infected worker bees and also tested whether infected bees were more attracted to, and consumed a greater proportion of, a diet containing propolis in comparison to uninfected bees. Propolis extracts and ethanol (solvent control) increased the lifespan of N. ceranae-infected bees, but only propolis extract significantly reduced spore load. Our propolis extract primarily contained derivatives of caffeic acid, ferulic acid, ellagic acid and quercetin. Choice, scan sampling and food consumption tests did not reveal any preference of N. ceranae-infected bees for commercial candy containing propolis. Our research supports the hypothesis that propolis represents an effective and safe product to control N. ceranae but worker bees seem not to use it to self-medicate when infected with this pathogen. Full article
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13 pages, 8904 KiB  
Article
How Does the Male Penisfilum Enter the Female Copulatory Pore in Hangingflies?
by Zheng Wei, Xin Tong and Bao-Zhen Hua
Insects 2020, 11(2), 123; https://doi.org/10.3390/insects11020123 - 14 Feb 2020
Cited by 5 | Viewed by 6340
Abstract
Hangingflies are characterized by the interesting nuptial feeding behavior and unusual belly-to-belly hanging mating position. However, the mating behavior and the copulatory mechanism remain poorly known for Bittacidae, especially how the elongated male penisfilum enters the copulatory pore of the female. In this [...] Read more.
Hangingflies are characterized by the interesting nuptial feeding behavior and unusual belly-to-belly hanging mating position. However, the mating behavior and the copulatory mechanism remain poorly known for Bittacidae, especially how the elongated male penisfilum enters the copulatory pore of the female. In this study, the mating behavior and copulatory mechanism of Terrobittacus implicatus (Huang and Hua, 2006) were investigated to reveal the functional morphology of hangingfly genitalia. The results show that the male provides a prey as a nuptial gift to the female and twists his abdomen about 180° to form a belly-to-belly hanging mating position. During the penisfilum-entering process, the male epandrial lobes clamp the female subgenital plate with the aid of the female abdomen swelling. Then the male locates the female copulatory pore through his upper branch of the proctiger and inserts his penisfilum into the female spermathecal duct in cooperation with the short setae on the groove of the proctiger. The female subgenital plate where the epandrial lobes clamp is strongly sclerotized and melanized. The copulatory mechanism of Terrobittacus is briefly discussed. Full article
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14 pages, 5833 KiB  
Article
Dispersibility of the Pale Grass Blue Butterfly Zizeeria maha (Lepidoptera: Lycaenidae) Revealed by One-Individual Tracking in the Field: Quantitative Comparisons between Subspecies and between Sexes
by Atsuki Hiyama and Joji M. Otaki
Insects 2020, 11(2), 122; https://doi.org/10.3390/insects11020122 - 14 Feb 2020
Cited by 7 | Viewed by 3327
Abstract
The pale grass blue butterfly Zizeeria maha (Lepidoptera: Lycaenidae) has been used as an environmental indicator species for radioactive pollution after the Fukushima nuclear accident. Here, based on the one-individual tracking method in the field, we examined dispersal-associated and other behavioral traits of [...] Read more.
The pale grass blue butterfly Zizeeria maha (Lepidoptera: Lycaenidae) has been used as an environmental indicator species for radioactive pollution after the Fukushima nuclear accident. Here, based on the one-individual tracking method in the field, we examined dispersal-associated and other behavioral traits of this butterfly, focusing on two subspecies, Z. maha argia in mainland Japan and Z. maha okinawana in Okinawa. The accumulated distances in the adult lifespan were 18.9 km and 38.2 km in mainland and Okinawa males, respectively, and 15.0 km and 7.8 km in mainland and Okinawa females, respectively. However, the mean distance from the starting point was only 24.2 m and 21.1 m in the mainland and Okinawa males, respectively, and 13.7 m and 7.4 m in the mainland and Okinawa females, respectively. Some quantitative differences in resting and feeding were found between subspecies and between sexes. The ARIMA (autoregressive integrated moving average) model indicated that the dispersal distance was 52.3 m (99% confidence interval value of 706.6 m) from the starting point in mainland males. These results support the idea that despite some behavioral differences, both subspecies of this butterfly are suitable as an environmental indicator because of the small dispersal ranges. Full article
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15 pages, 3053 KiB  
Article
The Roles of DNA Methyltransferases 1 (DNMT1) in Regulating Sexual Dimorphism in the Cotton Mealybug, Phenacoccus solenopsis
by Mohamed A.A. Omar, Meizhen Li, Feiling Liu, Kang He, Muhammad Qasim, Huamei Xiao, Mingxing Jiang and Fei Li
Insects 2020, 11(2), 121; https://doi.org/10.3390/insects11020121 - 12 Feb 2020
Cited by 11 | Viewed by 3986
Abstract
The cotton mealybug, Phenacoccus solenopsis, is an invasive pest that can cause massive damage to many host plants of agricultural importance. P. solenopsis is highly polyphagous, and shows extreme sexual dimorphism between males and females. The functions of DNA methyltransferase (DNMT) enzymes [...] Read more.
The cotton mealybug, Phenacoccus solenopsis, is an invasive pest that can cause massive damage to many host plants of agricultural importance. P. solenopsis is highly polyphagous, and shows extreme sexual dimorphism between males and females. The functions of DNA methyltransferase (DNMT) enzymes in the cotton mealybug have not been well studied. Here, we carried out an investigation of DNMTs in cotton mealybug to study their roles in sexual dimorphism. We found that the cotton mealybug has two copies of PsDnmt1, but Dnmt3 is absent. We then amplified the full-length cDNAs of PsDnmt1A (2225 bp) and PsDnmt1B (2862 bp) using rapid amplification cDNA ends (RACE). Quantitative reverse transcriptase PCR shows that both PsDnmt1A and PsDnmt1B are highly expressed in adult males, while the expression of PsDnmt1B is 30-fold higher in gravid females than in virgin females. We knocked down PsDnmt1A and PsDnmt1B with small interfering RNAs (siRNAs), and both genes were successfully down-regulated after 24 h or 72 h in adult females and pupa (t-test, p < 0.05). Down-regulating the expression of these two DNMT genes led to offspring lethality and abnormal body color in adult females. Furthermore, the silencing of PsDnmt1B induced abnormal wing development in emerged adult males. Our results provide evidence that PsDnmt1 plays a crucial role in regulating sexual dimorphism in the cotton mealybug. Full article
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22 pages, 11798 KiB  
Article
First Comprehensive Study of a Giant among the Insects, Titanus giganteus: Basic Facts from Its Biochemistry, Physiology, and Anatomy
by Jiří Dvořáček, Hana Sehadová, František Weyda, Aleš Tomčala, Markéta Hejníková and Dalibor Kodrík
Insects 2020, 11(2), 120; https://doi.org/10.3390/insects11020120 - 12 Feb 2020
Cited by 7 | Viewed by 5353
Abstract
Titanus giganteus is one of the largest insects in the world, but unfortunately, there is a lack of basic information about its biology. Previous papers have mostly described Titanus morphology or taxonomy, but studies concerning its anatomy and physiology are largely absent. Thus, [...] Read more.
Titanus giganteus is one of the largest insects in the world, but unfortunately, there is a lack of basic information about its biology. Previous papers have mostly described Titanus morphology or taxonomy, but studies concerning its anatomy and physiology are largely absent. Thus, we employed microscopic, physiological, and analytical methods to partially fill this gap. Our study focused on a detailed analysis of the antennal sensilla, where coeloconic sensilla, grouped into irregularly oval fields, and sensilla trichoidea were found. Further, the inspection of the internal organs showed apparent degeneration of the gut and almost total absence of fat body. The gut was already empty; however, certain activity of digestive enzymes was recorded. The brain was relatively small, and the ventral nerve cord consisted of three ganglia in the thorax and four ganglia in the abdomen. Each testis was composed of approximately 30 testicular follicles filled with a clearly visible sperm. Chromatographic analysis of lipids in the flight muscles showed the prevalence of storage lipids that contained 13 fatty acids, and oleic acid represented 60% of them. Some of our findings indicate that adult Titanus rely on previously accumulated reserves rather than feeding from the time of eclosion. Full article
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17 pages, 9212 KiB  
Article
Distribution of Galepsus spp. in Southern Africa and Life History of Galepsus lenticularis (Mantodea: Tarachodidae)
by Bianca Greyvenstein, Hannalene Du Plessis, Nicolas Moulin and Johnnie Van den Berg
Insects 2020, 11(2), 119; https://doi.org/10.3390/insects11020119 - 11 Feb 2020
Cited by 8 | Viewed by 4158
Abstract
Galepsus Stäl is a genus within the Mantodea and has hardly been studied in Africa. The distribution of the Galepsus genus in Southern Africa was established, based on insect collection records, and the biology of Galepsus (Lygdamia) lenticularis Saussure, was studied. [...] Read more.
Galepsus Stäl is a genus within the Mantodea and has hardly been studied in Africa. The distribution of the Galepsus genus in Southern Africa was established, based on insect collection records, and the biology of Galepsus (Lygdamia) lenticularis Saussure, was studied. In Southern Africa, 11 species of Galepsus were recorded. The first record of Galepsus (Onychogalepsus) centralis Beier, in South Africa was recorded during this study. The mean number of eggs per ootheca was 49.8 (±21.1) and unfertilized oothecae were significantly shorter and contained fewer eggs than hatched and unhatched oothecae, suggesting that females might invest fewer resources into production of oothecae that will not produce prodigy. No parthenogenesis was observed during this study. Although the mean duration of the male and female nymphal stages were similar, longevity of adult females (91.2 ± 35.0 days) was three times longer than that of males (26.3 ± 15.4 days). This phenomenon as well as the long period (20 ± 14.1 days) between oviposition of different oothecae, and duration of the incubation period (20.25 ± 6.3 days) suggests a survival strategy to reduce competition between siblings. Total longevity of males (166.9 ± 38.8) and females (252.9 ± 54.2) differed significantly. This study provides information on the distribution of Galepsus spp. in Southern Africa and describes the biology of G. lenticularis under captive breeding conditions, and contributes to the understanding of various biological aspects of G. lenticularis which has never been studied before. Full article
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16 pages, 2921 KiB  
Article
Phenology of the Diamondback Moth (Plutella xylostella) in the UK and Provision of Decision Support for Brassica Growers
by Charlotte Wainwright, Sascha Jenkins, Daniel Wilson, Marian Elliott, Andrew Jukes and Rosemary Collier
Insects 2020, 11(2), 118; https://doi.org/10.3390/insects11020118 - 11 Feb 2020
Cited by 14 | Viewed by 5474
Abstract
In the UK, severe infestations by Plutella xylostella occur sporadically and are due mainly to the immigration of moths. The aim of this study was to develop a more detailed understanding of the phenology of P. xylostella in the UK and investigate methods [...] Read more.
In the UK, severe infestations by Plutella xylostella occur sporadically and are due mainly to the immigration of moths. The aim of this study was to develop a more detailed understanding of the phenology of P. xylostella in the UK and investigate methods of monitoring moth activity, with the aim of providing warnings to growers. Plutella xylostella was monitored using pheromone traps, by counting immature stages on plants, and by accessing citizen science data (records of sightings of moths) from websites and Twitter. The likely origin of migrant moths was investigated by analysing historical weather data. The study confirmed that P. xylostella is a sporadic but important pest, and that very large numbers of moths can arrive suddenly, most often in early summer. Their immediate sources are countries in the western part of continental Europe. A network of pheromone traps, each containing a small camera sending images to a website, to monitor P. xylostella remotely provided accessible and timely information, but the particular system tested did not appear to catch many moths. In another approach, sightings by citizen scientists were summarised on a web page. These were accessed regularly by growers and, at present, this approach appears to be the most effective way of providing timely warnings. Full article
(This article belongs to the Collection Integrated Pest Management Strategies for Horticultural Crops)
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17 pages, 1886 KiB  
Article
Genetic Divergence of Two Sitobion avenae Biotypes on Barley and Wheat in China
by Da Wang, Xiaoqin Shi, Deguang Liu, Yujing Yang and Zheming Shang
Insects 2020, 11(2), 117; https://doi.org/10.3390/insects11020117 - 11 Feb 2020
Cited by 4 | Viewed by 2930
Abstract
Host plant affinity and geographic distance can play critical roles in the genetic divergence of insect herbivores and evolution of insect biotypes, but their relative importance in the divergence of insect populations is still poorly understood. We used microsatellite markers to test the [...] Read more.
Host plant affinity and geographic distance can play critical roles in the genetic divergence of insect herbivores and evolution of insect biotypes, but their relative importance in the divergence of insect populations is still poorly understood. We used microsatellite markers to test the effects of host plant species and geographic distance on divergence of two biotypes of the English grain aphid, Sitobion avenae (Fabricius). We found that clones of S. avenae from western provinces (i.e., Xinjiang, Gansu, Qinghai and Shaanxi) had significantly higher genetic diversity than those from eastern provinces (i.e., Anhui, Henan, Hubei, Zhejiang and Jiangsu), suggesting their differentiation between both areas. Based on genetic diversity and distance estimates, biotype 1 clones of eastern provinces showed high genetic divergence from those of western provinces in many cases. Western clones of S. avenae also showed higher genetic divergence among themselves than eastern clones. The Mantel test identified a significant isolation-by-distance (IBD) effect among different geographic populations of S. avenae, providing additional evidence for a critical role of geography in the genetic structure of both S. avenae biotypes. Genetic differentiation (i.e., FST) between the two biotypes was low in all provinces except Shaanxi. Surprisingly, in our analyses of molecular variance, non-significant genetic differentiation between both biotypes or between barley and wheat clones of S. avenae was identified, showing little contribution of host-plant associated differentiation to the divergence of both biotypes in this aphid. Thus, it is highly likely that the divergence of the two S. avenae biotypes involved more geographic isolation and selection of some form than host plant affinity. Our study can provide insights into understanding of genetic structure of insect populations and the divergence of insect biotypes. Full article
(This article belongs to the Special Issue Population Genetics of Insects)
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10 pages, 3947 KiB  
Article
Identification and Expression Patterns of Opsin Genes in a Forest Insect, Dendrolimus punctatus
by Sufang Zhang, Xiangbo Kong, Fu Liu and Zhen Zhang
Insects 2020, 11(2), 116; https://doi.org/10.3390/insects11020116 - 11 Feb 2020
Cited by 11 | Viewed by 2932
Abstract
Dendrolimus punctatus walker (Lepidoptera: Lasiocampidae) is the most serious coniferous forest defoliator in China. This species has long life history, and shows different activity rhythms and light response behaviors at larval and adult stages. Insect vision system play important roles for survival and [...] Read more.
Dendrolimus punctatus walker (Lepidoptera: Lasiocampidae) is the most serious coniferous forest defoliator in China. This species has long life history, and shows different activity rhythms and light response behaviors at larval and adult stages. Insect vision system play important roles for survival and reproduction, and disturbance of photoreception may help us to control this pest. However, we know little about the visual system of D. punctatus. As opsins are the most important genes determining photoreceptor sensitivity of insects, we identified opsins of D. punctatus and analyzed their expression patterns at different development stages in this study. Four opsin genes were identified based on our transcriptome data. Phylogenetic analysis showed that there are three classical ultraviolet (UV), blue, and long-wavelength (LW) light sensitive opsin genes, and another UV-like opsin as homolog of a circadian photoreceptor, Rh7, in Drosophila melanogaster and other insects. Expression analysis indicated that the UV and UV-like opsins expression levels only fluctuated slightly during whole life stages of D. punctatus, while Blue and LW opsins were up-regulated many times at adult stage. Interestingly, the ratio of UV-opsin was much higher in eggs and larvae stages, and lower in pupa and adult stages; reversely, LW-opsin showed extremely high relative ratio in pupa and adult stages. High expression level of LW opsin in the adult stage may correlate to the nocturnal lifestyles of this species at adult stage, and different ratios of UV and LW opsins in larval and adult stages may help to explain the different visual ecologies of these two development stages of D. punctatus. This work is the foundation for further research of opsin functions and vision mechanisms of D. punctatus. Full article
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10 pages, 1171 KiB  
Article
The Influence of Visual and Olfactory Cues in Host Selection for Bemisia tabaci Biotype B in the Presence or Absence of Tomato Yellow Leaf Curl Virus
by Nicholas Johnston and Xavier Martini
Insects 2020, 11(2), 115; https://doi.org/10.3390/insects11020115 - 11 Feb 2020
Cited by 26 | Viewed by 3511
Abstract
The silverleaf whitefly, Bemisia tabaci, is one of the most destructive agricultural pests in the world, vectoring a large number of devastating viruses, including Tomato Yellow Leaf Curl Virus (TYLCV). When selecting a host, B. tabaci is primarily influenced by a range [...] Read more.
The silverleaf whitefly, Bemisia tabaci, is one of the most destructive agricultural pests in the world, vectoring a large number of devastating viruses, including Tomato Yellow Leaf Curl Virus (TYLCV). When selecting a host, B. tabaci is primarily influenced by a range of visual and olfactory cues. Therefore, elucidating how such cues become modified in the presence of whitefly-vectored begomoviruses is critical to better understanding the epidemiology of many economically important diseases. The goal of this study was to determine how both visual and odor cues interact in the presence of TYLCV. In Y-tube olfactometer assays, whiteflies were submitted to a range of isolated visual and olfactory cues to determine behavioral changes. B. tabaci choices were then compared to both stimuli combined in the presence or absence of TYLCV. Under visual stimuli only, B. tabaci exhibited a visual attraction to the color yellow, TYLCV-infected tomato leaves, and TYLCV-infected tomato volatiles. Attraction was the strongest overall when both visual and olfactory cues from TYLCV-symptomatic tomato plants were combined, as opposed to a single isolated cue. These results highlight the importance of both sensory stimuli during B. tabaci host selection in the presence of an associated begomovirus. Full article
(This article belongs to the Special Issue The Study of Insect Movement and Foraging Strategies)
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11 pages, 272 KiB  
Article
Sulfoxaflor Residues in Pollen and Nectar of Cotton Applied through Drip Irrigation and Their Potential Exposure to Apis mellifera L.
by Hui Jiang, Jianjun Chen, Chen Zhao, Yongqing Tian, Zhixiang Zhang and Hanhong Xu
Insects 2020, 11(2), 114; https://doi.org/10.3390/insects11020114 - 10 Feb 2020
Cited by 21 | Viewed by 3366
Abstract
Systemic insecticides have been applied through drip irrigation for controlling crop pests, but few studies have addressed potential negative effects of the application on non-target organisms. In this study, the safety of sulfoxaflor applied at 450 or 700 g a.i. ha−1 [...] Read more.
Systemic insecticides have been applied through drip irrigation for controlling crop pests, but few studies have addressed potential negative effects of the application on non-target organisms. In this study, the safety of sulfoxaflor applied at 450 or 700 g a.i. ha−1 through drip irrigation at different times before flowering or during flowering to honey bee (Apis mellifera L.) was studied in 2016–2017 in a cotton production field in Xinjiang, China. Results showed that sulfoxaflor residues in pollen and nectar of cotton treated with sulfoxaflor at 450 g a.i. ha−1 before and during flowering through drip irrigation were either undetectable or no more than 17 μg·kg−1. Application of sulfoxaflor at 700 g a.i. ha−1 before flowering resulted in ≤ 14.2 μg·kg−1 of sulfoxaflor in pollen and < 0.68 μg·kg−1 in nectar. Sulfoxaflor applied at this higher rate during flowering had the highest residue, up to 39.2 μg·kg−1 in pollen and 13.8 μg·kg−1 in nectar. Risk assessments by contact exposure and dietary exposure showed that drip application of sulfoxaflor at the two rates before or during flowering posed little risk to honey bees. Thus, drip application of sulfoxaflor could represent an environmentally benign method for controlling cotton aphid. Full article
17 pages, 4050 KiB  
Article
Using RNA Interference to Reveal the Function of Chromatin Remodeling Factor ISWI in Temperature Tolerance in Bemisia tabaci Middle East–Asia Minor 1 Cryptic Species
by Shun-Xia Ji, Xiao-Di Wang, Xiao-Na Shen, Lin Liang, Wan-Xue Liu, Fang-Hao Wan and Zhi-Chuang Lü
Insects 2020, 11(2), 113; https://doi.org/10.3390/insects11020113 - 10 Feb 2020
Cited by 17 | Viewed by 3309
Abstract
Invasive species often encounter rapid environmental changes during invasions and only the individuals that successfully overcome environmental stresses can colonize and spread. Chromatin remodeling may be essential in environmental adaptation. To assess the functions of imitation switch (ISWI) in invasive Bemisia tabaci Middle [...] Read more.
Invasive species often encounter rapid environmental changes during invasions and only the individuals that successfully overcome environmental stresses can colonize and spread. Chromatin remodeling may be essential in environmental adaptation. To assess the functions of imitation switch (ISWI) in invasive Bemisia tabaci Middle East–Asia Minor 1 (MEAM1) cryptic species, we cloned and characterized the MEAM1 BtISWI gene and determined its functions in response to thermal stress. The full-length cDNA of BtISWI was 3712 bp, with a 3068 bp open reading frame (ORF) encoding a 118.86 kDa protein. BtISWI mRNA expression was significantly up-regulated after exposure to heat shock or cold shock conditions, indicating that BtISWI expression can be induced by thermal stress. After feeding double-stranded RNA (dsRNA), specifically for BtISWI, resistance to both heat and cold decreased significantly, suggesting that BtISWI may function directly in the thermal tolerance of MEAM1. Moreover, the preferred temperature of MEAM1 adults fed dsRNA was 1.9–3.5 °C higher than the control groups. Taken together, our findings highlight the importance of epigenetic gene regulation in the thermal response or thermal adaptation of invasive Bemisia tabaci (B. tabaci), and provide a new potential target for establishing sustainable control strategies for B. tabaci. Full article
(This article belongs to the Special Issue RNAi in Insect Pest Control)
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11 pages, 1327 KiB  
Article
Within-Stand Distribution of Tree Mortality Caused by Mountain Pine Beetle, Dendroctonus ponderosae Hopkins
by José F. Negrón
Insects 2020, 11(2), 112; https://doi.org/10.3390/insects11020112 - 10 Feb 2020
Cited by 4 | Viewed by 2243
Abstract
The mountain pine beetle (MPB) (Dendroctonus ponderosae) is a bark beetle that attacks and kills ponderosa pine (Pinus ponderosa), among other pine species throughout the western conifer forests of the United States and Canada, particularly in dense stands comprising [...] Read more.
The mountain pine beetle (MPB) (Dendroctonus ponderosae) is a bark beetle that attacks and kills ponderosa pine (Pinus ponderosa), among other pine species throughout the western conifer forests of the United States and Canada, particularly in dense stands comprising large trees. There is information on the stand conditions that the insect prefers. However, there is a paucity of information on how small-scale variation in stand conditions influences the distribution of tree mortality within a stand. I examined the small-scale distribution of ponderosa pine basal area pre- and post a mountain pine beetle infestation, and used geostatistical modeling to relate the spatial distribution of the host to subsequent MPB-caused tree mortality. Results indicated increased mortality in the denser parts of the stand. Previous land management has changed historically open low-elevation ponderosa pine stands with aggregated tree distribution into dense stands that are susceptible to mountain pine beetles and intense fires. Current restoration efforts are aimed at reducing tree density and leaving clumps of trees, which are more similar to historical conditions. The residual clumps, however, may be susceptible to mountain pine beetle populations. Land managers will want to be cognizant of how mountain pine beetles will respond to restoration treatments, so as to prevent and mitigate tree mortality that could negate restoration efforts. Full article
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14 pages, 3498 KiB  
Article
Invasion History of Sirex noctilio Based on COI Sequence: The First Six Years in China
by Xueting Sun, Jing Tao, Alain Roques and Youqing Luo
Insects 2020, 11(2), 111; https://doi.org/10.3390/insects11020111 - 9 Feb 2020
Cited by 4 | Viewed by 3060
Abstract
Sirex noctilio F. (Hymenoptera: Siricidae: Siricinae), a new invasive species in China, is a significant international forestry pest which, transported via logs and related wood packing materials, has led to environmental damage and substantial economic loss in many countries around the world. It [...] Read more.
Sirex noctilio F. (Hymenoptera: Siricidae: Siricinae), a new invasive species in China, is a significant international forestry pest which, transported via logs and related wood packing materials, has led to environmental damage and substantial economic loss in many countries around the world. It was first detected in China in 2013, and since then infestations have been found in 18 additional sites. Using a 322 bp fragment of the mitochondrial barcode gene COI, we studied the genetic diversity and structure of S. noctilio populations in both native and invaded ranges, with a specific focus in China. Twelve haplotypes were found across the native and invaded distribution of the pest, of which three were dominant; among these there were only one or two mutational steps between each pair of haplotypes. No obvious genetic structure was found other than in Chinese populations. China has a unique and dominant haplotype not found elsewhere, and compared with the rest of the world, the genetic structure of Chinese populations suggested a multiple invasion scenario. Full article
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