DEET and citronella oil are two of the most widely used mosquito repellents; however, their impact on chemosensory tissues is not fully understood. In their vapour phase, the repellency effect involves the olfactory system, with mosquitoes detecting and responding to diverse odorants through their antennae and mouthparts (maxillary palps and proboscis). In this study, we first performed repellency behavioural assays that indicated both DEET and citronella effectively impaired female Aedes aegypti host-seeking capabilities (i.e. landing on a host and taking a blood meal). We next used RNA sequencing to assess global gene expression changes in Ae. aegypti antennae, mouthparts and headless bodies in response to volatile repellent exposure. The resultant transcriptional changes were considerably greater in the mosquito mouthparts than in the other tissues. The most notable responses in olfactory-related genes to both repellents were the suppressed expression of the three subunits comprising the mosquito CO2 receptor (Gr1, 2 and 3). Genes associated with mitochondrial function and metabolism were also suppressed. Exposure to DEET was further characterized by substantial inhibition of cytochrome P450 mRNA expression, the primary detoxification enzymes in insects. Overall, our study provides novel insights into the olfactory and physiological responses of Ae. aegypti chemosensory tissues in response to DEET and citronella exposure.

Like other insects, coleopterans harbour dynamic bacteriomes that shape core aspects of their life history. The bacteriomes of several wireworm species (Coleoptera: Elateridae) have been described; however, little research has been undertaken to determine the factors that influence their structure and composition. These soil-dwelling larvae of click beetles are significant agricultural pests in the Canadian Prairies, with the most ubiquitous species, Hypnoidus bicolor, delineated into two genetically distinct clades and both sexual and parthenogenetic populations. In this study, we collected 69 H. bicolor adults and larvae from nine populations spanning three Prairie provinces and subjected them to Sanger and 16S rRNA gene sequencing to determine their clade and characterize their bacteriome, respectively. Combined with long-term surveillance, we provide compelling evidence that the parthenogenetic and sexual populations are associated with different clades. Development, sampling location and host genetics all contributed to the plasticity of H. bicolor bacteriomes. These differences are largely attributed to gut bacterial community composition of larvae, whereas, in adults, they appear driven by overall community structure as well as differences in the presence/absence of taxa and within-clade/population variance. Several notable genera emerged from our study, including Alphaproteobacteria and Rickettsiella endosymbionts that predominated in the parthenogenetic clade. Incorporation of this research into integrative pest management and reclassification of H. bicolor into a cryptic species complex is also discussed. Overall, this study advances our understanding of Elateridae bacteriomes, including factors that contribute to their richness and community composition.

A growing number of plastivore insects have been discovered that readily consume and biodegrade various petro plastics, including LDPE. The caterpillar larvae of Galleria mellonella are capable of breaking down the polymers at expedited rates; however, feeding on LDPE as a sole nutrient source is inefficient and detrimentally impacts larval survival, growth, and development. The objective of our study was to improve fitness parameters and feeding activities of LDPE-fed larvae through the addition of various macro- and micronutrients. Each co-supplementation recovered fitness and consumption to some extent in comparison to pure LDPE; however, artificial sources produced outcomes that were well below those of the caterpillar's natural diet, regardless of the combination. Co-supplementation of LDPE, honeycomb, and corn syrup was the most successful, with larval fitness and consumption approximating their natural diet. To provide mechanistic insights into this recovery, qPCR and metagenomics analyses indicated the co-supplementation promoted greater gut bacterial abundance and species richness and evenness. In addition, GC-MS analyses identified notable differences in their fat body metabolic profiles that may contribute to slower developmental rates. We also assessed the capability of the larvae to eliminate food wastes, which showed promise and could represent a potential co-supplement source for LDPE biodegradation.

A significant emphasis of insect symbiont research has focused on the digestive tract and elucidating whether bacteria colonize and proliferate or transiently pass through is integral to our understanding of microbial community structure and host-microbe interactions. The larval stages of the greater wax moth, Galleria mellonella Fabricius (Lepidoptera: Pyralidae), have become increasingly used in studies that are heavily influenced by host-microbiome dynamics (e.g., plastic biodegradation and innate immunity). However, it is presently unclear whether continual bacterial recruitment is required to sustain the bacterial assemblages, and the extent by which gut bacterial flora is a reflection of their food substrate. Therefore, the objective of this study was to discern between transient and more persistent gut microbes harbored by G. mellonella larvae, and to evaluate their relative contributions to microbial diversity and abundance. We used 16S rRNA sequencing to characterize and compare the bacteriomes of G. mellonella to their natural honeycomb diet throughout larval development, as well as to caterpillars subjected to a 4-day starvation period. Then, we used qPCR to measure relative bacterial abundances at each instar. Our results indicate larval gut bacterial composition and abundance are predominantly diet-driven, with a myriad of bacterial genera seemingly transiently present. However, several genera (e.g., Ralstonia, Pelomonas, and Cutibacterium) appear to be more permanent fixtures, presumably colonizing and proliferating in the digestive tract. Moreover, some bacterial genera co-occur, forming non-random associations that may be indicative of functional synergies. Overall, this study advances our knowledge of lepidopteran gut microbial dynamics and provides valuable information for an emerging invertebrate model.

Nearly all insects harbour bacterial communities that can have a profound effect on their life history, including regulating and shaping host metabolism, development, immunity and fitness. The bacteriomes of several coleopterans have been described; however, very little has been reported for wireworms. These long-lived larvae of click beetles (Coleoptera: Elateridae) are major agricultural pests of a variety of crops grown in the Canadian Prairies. Consequently, the goal of this study was to characterise the bacteriomes of five of the most significant pest species within the region: Limonius californicus, Hypnoidus abbreviatus, H. bicolor, Aeolus mellillus and Dalopius spp. To do this, we collected larvae from southern Manitoba fields (pre-seeding) and carried out 16S rRNA sequencing on individual specimens. Our results indicate wireworms have diverse and taxon-rich bacterial communities, with over 400 genera identified predominately from the phyla Proteobacteria, Actinobacteriota, Bacteroidota and Firmicutes. However, each species had nine or fewer genera comprising >80% of their bacteriome. Network analyses revealed some community structuring consistent among species, which may culminate in shaping/regulating host biology. Moreover, the microbial signatures were influenced by both ontogeny (early vs. late stage larvae) and reproductive strategy (sexual vs. parthenogenetic), with a myriad of other factors likely contributing to bacterial diversity that are impossible to resolve from our study. Overall, this metagenomics study represents the first to characterise the bacteriomes of wireworms in the Canadian Prairies and the findings could assist in the development of sustainable management strategies for these important agricultural pests.

Important agricultural pests in the Canadian Prairies, wireworms are the soil-living larvae of click beetles. Several notable species are found within the Prairies, with Hypnoidus bicolor being the most ubiquitous in most parts of the region. Despite their prevalence, H. bicolor is often disregarded as a significant pest species due to their comparatively small larval sizes. However, few studies have directly assessed the capacity of wireworms to cause damage to particular crop(s), and thus far no such studies have been undertaken for H. bicolor . We therefore carried out laboratory experiments under controlled environmental conditions, with soil and wireworms transplanted from the field, to determine the capability of H. bicolor to damage soybean. As expected, wireworm damage was strongly associated with larval densities, with more severe soybean injury occurring in the presence of greater numbers of H. bicolor . Further, feeding damage to soybean by H. bicolor was greater at lower temperatures (10 °C and 20 °C) than at higher temperatures (30 °C). In terms of soil texture, soybean grown in loam and silt soils were the most susceptible to wireworm damage and those grown in clay soil were the least affected. Although the larvae are not capable of damaging soybean to the same extent as other Prairie pest species, Limonius californicus and Hypnoidus abbreviatus , in high enough densities and under ideal environmental conditions H. bicolor can significantly impact soybean growth. Overall, our study suggests that soybean is susceptible to considerable wireworm damage and H. bicolor is an under recognized pest species of this legume.

BACKGROUND The long-lived terricolous larvae of click beetles, colloquially called wireworms, pose a significant threat to agriculture worldwide. Several economically important pest species have been documented in the Canadian Prairies, including Hypnoidus bicolor, Limonius californicus and Hypnoidus abbreviatus. However, most monitoring activities are performed in the early spring and there is evidence from other geographical regions of seasonal shifts in wireworm species composition and prevalence. Further, little is known about the overwintering physiology or behaviors of wireworms, which undoubtedly contribute to their population dynamics. RESULTS We surveyed wireworm populations from four Manitoban fields six times throughout the 2020 and 2021 growing seasons. Both Hypnoidus species were active throughout the spring and summer; however, L. californicus did not become active until later in the spring. Chill-coma recovery assays indicated Hypnoidus species recovered quicker than L. californicus from cold acclimation. Vertical migration assays simulating progressively lower ambient temperatures experienced by overwintering larvae identified H. bicolor throughout the soil profile, with L. californicus preferentially found at cooler, shallower depths. We speculate that these differences in species distribution within the soil column are due to the higher levels of putative cryoprotectants (for example, trehalose, sorbitol, glucose, glycerol) in L. californicus, as identified by targeted liquid chromatography tandem mass spectrometry. CONCLUSION Our findings of a stark seasonal turnover in wireworm species prevalence and composition in the Canadian Prairies should be incorporated into future integrated pest management and surveillance activities. This study also advances our understanding of wireworm overwintering biology, which should be factored into current management approaches. (c) 2022 His Majesty the King in Right of Canada. Pest Management Science (c) 2022 Society of Chemical Industry. Reproduced with the permission of the Minister of Agriculture and Agri-Food Canada.

BACKGROUND Wireworms, the soil-dwelling larvae of click beetles, are a major threat to global agricultural production. This is largely due to their generalist polyphagous feeding capabilities, extended and cryptic life cycles, and limited management options available. Although wireworms are well-documented as economically important pests in the Canadian Prairies, including Manitoba, there are gaps in knowledge on species distributions, subterranean behaviour and life cycles, feeding ecology and damage capacity, and economic thresholds for crop yield loss. Results We carried out 3 years (2018-2020) of intensive surveillance of larval populations across Manitoba. A total of 31 fields (24 in >= 2 consecutive years) were surveyed in early spring using standardized bait trapping approaches. Wireworms were present in 94% of surveyed sites, but the catch within fields varied year to year. While Hypnoidus bicolor predominated (94% of larvae), several other pest species were identified. We then explored the relationships between wireworm trap numbers and agro-environmental factors. The larval catch tended to decrease under conditions of low soil temperatures and increased clay content, coupled with high soil moisture and precipitation during the trapping period. Treatment and cultural methods appeared less influential; however, wheat production in either of the previous two growing seasons was associated with increased wireworm catch. Our models failed to predict a relationship between wireworm catch and crop yields, although infestations were rare in our region. Conclusion Our findings better infer the risks posed by wireworms to crop production in the Canadian Prairies, and the agro-environmental factors that represent the greatest contributors to these risks. This information should be incorporated into future integrated pest management (IPM) strategies for wireworms.

Wireworms are significant pests of a variety of economically important crops grown in the Canadian Prairies. These soil-dwelling larvae of click beetles feed on and burrow into the accessible underground plant tissues, which can result in cosmetic injury, stunting, wilting, and plant death. Successful management of wireworms relies on accurate estimations of their abundance and activity in infested fields. Bait trapping is the most commonly used method for sampling wireworms and standardized approaches have been developed; however, little work has been done to optimize trapping efficacy in different geographical regions. In this study, we evaluated the effect of bait trapping duration, seed formulation, and the causal relationship with CO2 production and soil temperature on the wireworm catch in three fields located in Manitoba, Canada. As expected, wireworm catch increased with trapping duration and placing traps in ground for 8 d is adequate in most cases. Both barley and wheat were more effective baits than soybean; however, barley released more CO2 (i.e., an attractant for wireworms) and performed better at elevated soil temperatures. Overall, the results of this study will serve as valuable guidelines to improve current wireworm sampling methods, and can be integrated into strategies aimed at managing these important pests to crop production.

BACKGROUND Following banning of the pesticide lindane in most counties, wireworms (i.e., the soil-living larval stages of click beetles) have become major pests of a variety of economically important field crops. Hypnoidus bicolor is a common pest species in the Canadian Prairies. However, little is known about its life history, which impedes the development of effective integrated pest management (IPM) strategies. Population genetic approaches have the potential to assist in the development of IPM. RESULTS We sequenced a 622-bp fragment of the COX1 gene from 326 H. bicolor wireworm and click beetles collected from 13 localities on the Canadian Prairies. Two genetically distinct (>4.66% sequence divergence) clades were identified, suggesting that they may be part of a species complex. Clade A predominated and increased in prevalence the further east samples were collected, whereas the opposite was true for clade B. Clade B appears to be comprised of two mitochondrial DNA groups, however, one group was represented by only one haplotype. Both clades were characterized by uneven gene flow among populations with low levels of regional genetic structuring. Clade A appeared to have undergone population and range expansions, which may coincide with the advent of intensive agriculture practices in the prairies. CONCLUSION Knowledge of species composition and population structure is important for the development of effective IPM strategies but is often lacking for wireworms. Our study fills these knowledge gaps for a predominant pest species in the prairies, H. bicolor, by providing robust evidence for cryptic forms and characterizing its dispersal patterns and population dynamics.

Native to the Eastern United States and Eastern Canada, Aedes triseriatus (eastern tree hole mosquito) is an important vector of La Crosse virus and dog heartworm. Although its range has been well characterized in the United States, few studies have surveyed its distribution within Canada. In this study, mosquitoes were collected from a variety of urban and rural communities throughout Manitoba, Canada between the years of 2018 and 2020. Aedes triseriatus was identified and confirmed molecularly to be present in 13 communities. This includes localities that expand the species known distribution to new northern and western areas, and suggests that past surveillance efforts have not been comprehensive or environmental factors have caused this mosquito species to be present in areas in which it was not found previously. As Canada is showing signs of a changing climate, this may be driving the broader occurrence of Ae. triseriatus.