Temporal resource continuity for egg parasitoids of Dalbulus maidis (Hemiptera: Cicadellidae) during winter on irrigated maize crops and edge grasses.

Little is known about winter-season parasitism of eggs of the corn leafhopper Dalbulus maidis DeLong (Hemiptera: Cicadellidae), an important pest of maize throughout the Americas. Our study, conducted in Mexico, aimed to characterize winter-season parasitism of corn leafhopper eggs on maize crops cultivated with drip irrigation and on wild grasses that grow on the edges of maize crops when maize is not present. Maize leaves baited with D. maidis eggs were used to trap the egg parasitoids in the field. In the first year (2022), parasitism of D. maidis eggs was investigated in maize fields planted contiguously on different dates (asynchronous planting). In the second year (2023), parasitism of D. maidis eggs was evaluated in edge grasses and in adjacent maize crops planted on the same date (synchronous). The highest percentage of parasitism (53%), percentage of emergence, and total abundance of egg parasitoids were found in asynchronous maize fields. Here, Anagrus virlai Triapitsyn (Hymenoptera: Mymaridae), Paracentrobia subflava (Girault) (Hymenoptera: Trichogrammatidae), and Pseudoligosita sp. (Hymenoptera: Trichogrammatidae) wasps were found parasitizing the D. maidis eggs, with P. subflava being the most abundant. In wild edge grasses, only P. subflava was found, showing low levels of parasitism, while in synchronous maize, P. subflava increased its percentage of parasitism (up to 37%), percentage of emergence, and abundance, during winter. These results suggest that P. subflava acts as an efficient biological control agent of D. maidis in irrigation-grown maize crops during the winter season, and that edge grasses are overwinter habitats for P. subflava.

Diversity analyses of bacterial symbionts in four Sclerodermus (Hymenoptera: Bethylidae) parasitic wasps, the dominant biological control agents of wood-boring beetles in China.

Objective: Sclerodermus wasps are important biocontrol agents of a class of wood borers. Bacterial symbionts influence the ecology and biology of their hosts in a variety of ways, including the formation of life-long beneficial or detrimental parasitic infections. However, only a few studies have explored the species and content of the symbionts in the Sclerodermus species. Methods: Here, a high-throughput sequencing study of the V3-V4 region of the 16S ribosomal RNA gene revealed a high level of microbial variety in four Sclerodermus waps, and their diversities and functions were also predicted. Results: The three most prevalent phyla of microorganisms in the sample were Firmicutes, Bacteroides, and Proteus. The KEEG pathways prediction results indicated that the three pathways with the highest relative abundances in the S. sichuanensis species were translation, membrane transport, and nucleotide metabolism. These pathways differed from those observed in S. guani, S. pupariae, and S. alternatusi, which exhibited carbohydrate metabolism, membrane transport, and amino acid metabolism, respectively. Bacteroides were found to be abundant in several species, whereas Wolbachia was the most abundant among S. sichuanensis, with a significant negative correlation between temperature and carriage rate. Conclusions: These results offer insights into the microbial communities associated with the bethylid wasps, which is crucial for understanding how to increase the reproductive capacity of wasps, enhance their parasitic effects, and lower cost in biocontrol.

Host and venom evolution in parasitoid wasps: does independently adapting to the same host shape the evolution of the venom gland transcriptome?

BACKGROUND: Venoms have repeatedly evolved over 100 occasions throughout the animal tree of life, making them excellent systems for exploring convergent evolutionary novelty. Growing evidence supports that venom evolution is predominantly driven by prey or host-related selection pressures, and the expression patterns of venom glands reflect adaptive evolution. However, it remains elusive whether the evolution of expression patterns in venom glands is likewise a convergent evolution driven by their prey/host species. RESULTS: We utilized parasitoid wasps that had independently adapted to Drosophila hosts as models to investigate the convergent evolution of venom gland transcriptomes in 19 hymenopteran species spanning ~ 200 million years of evolution. Comparative transcriptome analysis reveals that the global expression patterns among the venom glands of Drosophila parasitoid wasps do not achieve higher similarity compared to non-Drosophila parasitoid wasps. Further evolutionary analyses of expression patterns at the single gene, orthogroup, and Gene Ontology (GO) term levels indicate that some orthogroups/GO terms show correlation with the Drosophila parasitoid wasps. However, these groups rarely include genes highly expressed in venom glands or putative venom genes in the Drosophila parasitoid wasps. CONCLUSIONS: Our study suggests that convergent evolution may not play a predominant force shaping gene expression levels in the venom gland of the Drosophila parasitoid wasps, offering novel insights into the co-evolution between venom and prey/host.

Design and evaluation of a pneumatic actuation unit for a wasp-inspired self-propelled needle.

Transperineal laser ablation is a minimally invasive thermo-ablative treatment for prostate cancer that requires the insertion of a needle for accurate optical fiber positioning. Needle insertion in soft tissues may cause tissue motion and deformation, resulting in tissue damage and needle positioning errors. In this study, we present a wasp-inspired self-propelled needle that uses pneumatic actuation to move forward with zero external push force, thus avoiding large tissue motion and deformation. The needle consists of six parallel 0.25-mm diameter Nitinol rods driven by a pneumatic actuation system. The pneumatic actuation system consists of Magnetic Resonance (MR) safe 3D-printed parts and off-the-shelf plastic screws. A self-propelled motion is achieved by advancing the needle segments one by one, followed by retracting them simultaneously. The advancing needle segment has to overcome a cutting and friction force, while the stationary needle segments experience a friction force in the opposite direction. The needle self-propels through the tissue when the friction force of the five stationary needle segments overcomes the sum of the friction and cutting forces of the advancing needle segment. We evaluated the prototype's performance in 10-wt% gelatin phantoms and ex vivo porcine liver tissue inside a preclinical Magnetic Resonance Imaging (MRI) scanner in terms of the slip ratio of the needle with respect to the phantom or liver tissue. Our results demonstrated that the needle was able to self-propel through the phantom and liver tissue with slip ratios of 0.912-0.955 and 0.88, respectively. The prototype is a promising step toward the development of self-propelled needles for MRI-guided transperineal laser ablation as a method to treat prostate cancer.

A molecular approach to unravel trophic interactions between parasitoids and hyperparasitoids associated with pecan aphids.

Advances in molecular ecology can overcome many challenges in understanding host-parasitoid interactions. Genetic characterization of the key-players in systems helps to confirm species and identify trophic linkages essential for ecological service delivery by biological control agents; however, relatively few agroecosystems have been explored using this approach. Pecan production consists of a large tree perennial system containing an assortment of seasonal pests and natural enemies. As a first step to characterizing host-parasitoid associations in pecan food webs, we focus on aphid species and their parasitoids. Based on DNA barcoding of field-collected and reared specimens, we confirmed the presence of 3 species of aphid, one family of primary parasitoids, and 5 species of hyperparasitoids. By applying metabarcoding to field-collected aphid mummies, we were able to identify multiple species within each aphid mummy to unravel a complex food web of 3 aphids, 2 primary parasitoids, and upward of 8 hyperparasitoid species. The results of this study demonstrate that multiple hyperparasitoid species attack a single primary parasitoid of pecan aphids, which may have negative consequences for successful aphid biological control. Although further research is needed on a broader spatial scale, our results suggest multiple species exist in this system and may suggest a complex set of interactions between parasitoids, hyperparasitoids, and the 3 aphid species. This was the first time that many of these species have been characterized and demonstrates the application of novel approaches to analyze the aphid-parasitoid food webs in pecans and other tree crop systems.

Real-time dynamics of aculeate hymenopteran reed gall inquilines in oligotrophic reed beds of anthropogenic and natural origin.

This is the first study providing long-term data on the dynamics of bees and wasps and their parasitoids for the evidence-based management of reed beds. Ten years ago, we identified Lipara (Chloropidae) - induced galls on common reed (Phragmites australis, Poaceae) as a critically important resource for specialized bees and wasps (Hymenoptera: Aculeata). We found that they were surprisingly common in relatively newly formed anthropogenic habitats, which elicited questions about the dynamics of bees and wasps and their parasitoids in newly formed reed beds of anthropogenic origin. Therefore, in the winter and spring of 2022/23, we sampled reed galls from the same set of reed beds of anthropogenic and natural origin as those in 2012/13. At 10 sites, the number of sampled galls was similar in both time periods (80-122% of the value from 2012/13); 12 sites experienced a moderate decline (30-79% of the value from 2012/13), and the number of galls at six sampling sites was only 3-23% of their abundance in 2012/13. Spontaneous development was associated with increasing populations. After 10 years of spontaneous development, the populations of bees and wasps (including their parasitoids) bound to Lipara-induced reed galls increased in abundance and species richness or remained at their previous levels, which was dependent on the sampling site. The only identified threat consisted of reclamation efforts. The effects of habitat age were limited, and the assemblages in habitats of near-natural and anthropogenic origin largely overlapped. However, several species were consistently present at lower abundances in the anthropogenic habitats and vice versa. In conclusion, we provided evidence-based support for the establishment of oligotrophic reed beds of anthropogenic origin as management tools providing sustainable habitats for specialized reed gall-associated aculeate hymenopteran inquilines, including the threatened species.

Nesting Biology of Megachile (Chrysosarus) jenseni (Hymenoptera: Megachilidae) in Two Contrasting Pampean Agroecosystems: A Potential Pollinator for Alfalfa?

Several crops depend on both managed and wild bees to produce fruits and/or seeds, and the efficiency of numerous wild bees is higher than that of some managed species. Therefore, knowing and understanding the required resources for wild bees could enabled the establishment of management practices to increase their populations. Here, we provide information about the nesting biology of Megachile (Chrysosarus) jenseni, a Faboideae-specialist bee species. Based on observations from two populations occurring in contrasting agroecosystems, this bivoltine species showed common behavioral features shared with other species of subgenus Chrysosarus, such as the use of petal pieces and mud as nesting materials and the utilization of pre-existing cavities. Both studied populations showed a bivoltine life cycle with a rapid early-summer generation and a second generation, with most individuals overwintering. Main causes of mortality were unknown diseases (or other factors), causing the death of preimaginal stages. Moreover, this species was attacked by a cleptoparasite megachilid (Coelioxys remissa), a parasitic eulophid wasp (Melittobia sp.), and a bee fly (Anthrax oedipus). Finally, we discussed the potential use of this leaf-cutter bee species for alfalfa pollination.

Reinforced colour preference of parasitoid wasps in the presence of floral scent: a case study of a cross-modal effect.

We examined the possibility of a cross-modal effect in naïve Cotesia vestalis, a parasitoid wasp of diamondback moth larvae, by using artificial flower models of four colours (blue, green, yellow, and red) in the absence or presence of floral scent collected from Brassica rapa inflorescences. In a four-choice test, regardless of the floral scent, non-starved female wasps visited green and yellow models significantly more often than blue and red ones, although no significant difference was observed between visits to the green and yellow models. They seldom visited blue and red models. When starved, the wasps became even more particular, visiting yellow significantly more frequently than green models, irrespective of the presence of the floral scent, indicating that they preferred to use yellow visual cues in their food search. Furthermore, a factorial analysis of variance revealed a significant effect of the interaction between model colour and floral scent on the wasps' visits to flower models. The floral scent induced starved and non-starved wasps to visit yellow and green models about twice as often as without the scent. A cross-modal effect of olfactory perception on the use of chromatic information by wasps may allow them to search efficiently for food sources.

Female-Biased Odorant Receptor MmedOR48 in the Parasitoid Microplitis mediator Broadly Tunes to Plant Volatiles.

Odorant receptors (ORs) play a crucial role in insect chemoreception. Here, a female-biased odorant receptor MmedOR48 in parasitoid Microplitis mediator was fully functionally characterized. The qPCR analysis suggested that the expression level of MmedOR48 increased significantly after adult emergence and was expressed much more in the antennae. Moreover, an in situ hybridization assay showed MmedOR48 was extensively located in the olfactory sensory neurons. In two-electrode voltage clamp recordings, recombinant MmedOR48 was broadly tuned to 23 kinds of volatiles, among which five plant aldehyde volatiles excited the strongest current recording values. Subsequent molecular docking analysis coupled with site-directed mutagenesis demonstrated that key amino acid residues Thr142, Gln80, Gln282, and Thr312 together formed the binding site in the active pocket for the typical aldehyde ligands. Furthermore, ligands of MmedOR48 could stimulate electrophysiological activities in female adults of the M. mediator. The main aldehyde ligand, nonanal, aroused significant behavioral preference of M. mediator in females than in males. These findings suggest that MmedOR48 may be involved in the recognition of plant volatiles in M. mediator, which provides valuable insight into understanding the olfactory mechanisms of parasitoids.

Pest management facing warming and chemical stresses: Multi-stress effects on the biological agent Trichogramma oleae.

Global change is affecting plant-insect interactions in agroecosystems and can have dramatic consequences on yields when causing non-targeted pest outbreaks and threatening the use of pest natural enemies for biocontrol. The vineyard agroecosystem is an interesting system to study multi-stress conditions: on the one hand, agricultural intensification comes with high inputs of copper-based fungicides and, on the other hand, temperatures are rising due to climate change. We investigated interactive and bottom-up effects of both temperature increase and copper-based fungicides exposure on the important Lepidopteran vineyard pest Lobesia botrana and its natural enemy, the oophagous parasitoid Trichogramma oleae. We exposed L. botrana larvae to three increasing copper sulfate concentrations under two fluctuating thermal regimes, one current and one future. Eggs produced by L. botrana were then exposed to T. oleae. Our results showed that the survival of L. botrana, was only reduced by the highest copper sulfate concentration and improved under the warmer regime. The development time of L. botrana was strongly reduced by the warmer regime but increased with increasing copper sulfate concentrations, whereas pupal mass was reduced by both thermal regime and copper sulfate. T. oleae F1 emergence rate was reduced and their development time increased by combined effects of the warmer regime and increasing copper sulfate concentrations. Size, longevity and fecundity of T. oleae F1 decreased with high copper sulfate concentrations. These effects on the moth pest and its natural enemy are probably the result of trade-offs between the survival and the development of L. botrana facing multi-stress conditions and implicate potential consequences for future biological pest control. Our study supplies valuable data on how the interaction between pests and biological control agents is affected by multi-stress conditions.

Species richness estimation of the Afrotropical Darwin wasps (Hymenoptera, Ichneumonidae).

Species richness is one of the fundamental metrics of biodiversity. Estimating species richness helps spotlight taxonomic groups that are particularly under-studied, such as the highly diverse Darwin wasps. The only available estimate of the number of Darwin wasps in the Afrotropics proposed almost 11,000 species, compared to the 2,322 recorded species. However, it relied exclusively on the ratio of morphospecies to described species in Henry Townes' personal collection. We provide an updated estimate of the Afrotropical Darwin wasp species, using empirical data from multiple sources, including the increase in species numbers following generic revisions, morphospecies sorting in natural history collections, and diversity patterns of better-studied insects (butterflies) for extrapolation. Our analyses suggest that our knowledge of Darwin wasps is highly incomplete, with only 13-22% of species known in the five most extensively studied countries in the Afrotropics. We estimate 9,206-15,577 species of Darwin wasps within the entire Afrotropics, with the highest concentration expected in the Equatorial Afrotropics and Madagascar. Due to data constraints, our approach tends to underestimate diversity at each step, rendering the upper estimate (15,577 species) more realistic. We highlight reasons contributing to the gap between recorded and estimated species richness, including logistical and financial factors, as well as post-colonial influences.

Unraveling climatic niche evolution: Insights into the geographical distribution of the neotropical social wasp genus Synoeca (Hymenoptera, Vespidae, Epiponini).

Niche evolution refers to the process by which species undergo changes in ecological interactions, as well as their ability to disperse over time. Our study focuses on the widely distributed neotropical genus of social wasps, Synoeca (Hymenoptera, Vespidae, Epiponini). We use ecological niche modeling to investigate the niche evolution of this insects, to explore how species have evolved within and across distinct environmental boundaries, as well as to explore the overlap, equivalence, and similarity between their niches. Our analysis of Predicted Niche Occupancy reveals that species occupy heterogeneous niches in relation to temperature, precipitation, and altitude, similar to the patterns observed in the analysis of the evolutionary history of climate tolerances, which shows that species have evolved to occupy distinct niche ranges. In addition, our niche comparisons indicate that the species do not share similar niches with each other. All these results suggest that Phylogenetic Niche Conservatism may be playing a significant role as a process contributing to the allopatric pattern observed in this genus. This study represents the first investigation of niche evolution in Vespidae, providing valuable insights for future research into the evolutionary dynamics of insects.

Coordinated molecular and ecological adaptations underlie a highly successful parasitoid.

The success of an organism depends on the molecular and ecological adaptations that promote its beneficial fitness. Parasitoids are valuable biocontrol agents for successfully managing agricultural pests, and they have evolved diversified strategies to adapt to both the physiological condition of hosts and the competition of other parasitoids. Here, we deconstructed the parasitic strategies in a highly successful parasitoid, Trichopria drosophilae, which parasitizes a broad range of Drosophila hosts, including the globally invasive species D. suzukii. We found that T. drosophilae had developed specialized venom proteins that arrest host development to obtain more nutrients via secreting tissue inhibitors of metalloproteinases (TIMPs), as well as a unique type of cell-teratocytes-that digest host tissues for feeding by releasing trypsin proteins. In addition to the molecular adaptations that optimize nutritional uptake, this pupal parasitoid has evolved ecologically adaptive strategies including the conditional tolerance of intraspecific competition to enhance parasitic success in older hosts and the obligate avoidance of interspecific competition with larval parasitoids. Our study not only demystifies how parasitoids weaponize themselves to colonize formidable hosts but also provided empirical evidence of the intricate coordination between the molecular and ecological adaptations that drive evolutionary success.

Molecular Characterization of Chemosensory Protein (CSP) Genes and the Involvement of AgifCSP5 in the Perception of Host Location in the Aphid Parasitoid Aphidius gifuensis.

Aphidius gifuensis is the dominant parasitic natural enemy of aphids. Elucidating the molecular mechanism of host recognition of A. gifuensis would improve its biological control effect. Chemosensory proteins (CSPs) play a crucial role in insect olfactory systems and are mainly involved in host localization. In this study, a total of nine CSPs of A. gifuensis with complete open reading frames were identified based on antennal transcriptome data. Phylogenetic analysis revealed that AgifCSPs were mainly clustered into three subgroups (AgifCSP1/2/7/8, AgifCSP3/9, and AgifCSP4/5/6). AgifCSP2/5 showed high expression in the antennae of both sexes. Moreover, AgifCSP5 was found to be specifically expressed in the antennae. In addition, fluorescent binding assays revealed that AifCSP5 had greater affinities for 7 of 32 volatile odor molecules from various sources. Molecular docking and site-directed mutagenesis results revealed that the residue at which AgifCSP5 binds to these seven plant volatiles is Tyr75. Behavior tests further confirmed that trans-2-nonenal, one of the seven active volatiles in the ligand binding test, significantly attracted female adults at a relatively low concentration of 10 mg/mL. In conclusion, AgifCSP5 may be involved in locating aphid-infested crops from long distances by detecting and binding trans-2-nonenal. These findings provide a theoretical foundation for further understanding the olfactory recognition mechanisms and indirect aphid localization behavior of A. gifuensis from long distances by first identifying the host plant of aphids.

Comparative transcriptome reprogramming in oak galls containing asexual or sexual generations of gall wasps.

Oak gall wasps have evolved strategies to manipulate the developmental pathways of their host to induce gall formation. This provides shelter and nutrients for the developing larva. Galls are entirely host tissue; however, the initiation, development, and physical appearance are controlled by the inducer. The underlying molecular mechanisms of gall formation, by which one or a small number of cells are reprogrammed and commit to a novel developmental path, are poorly understood. In this study, we sought a deeper insight into the molecular underpinnings of this process. Oak gall wasps have two generations each year, one sexual, and one asexual. Galls formed by these two generations exhibit a markedly different appearance. We sequenced transcriptomes of both the asexual and sexual generations of Neuroterus quercusbaccarum and Neuroterus numismalis. We then deployed Nanopore sequencing to generate long-read sequences to test the hypothesis that gall wasps introduce DNA insertions to determine gall development. We detected potential genome rearrangements but did not uncover any non-host DNA insertions. Transcriptome analysis revealed that transcriptomes of the sexual generations of distinct species of wasp are more similar than inter-generational comparisons from the same species of wasp. Our results highlight the intricate interplay between the host leaves and gall development, suggesting that season and requirements of the gall structure play a larger role than species in controlling gall development and structure.

Odorant-binding protein CrufOBP1 in Cotesia ruficrus females plays a pivotal role in the detection of Spodoptera frugiperda larvae.

Cotesia ruficrus presents a promising local natural enemy for controlling the invasive fall armyworm Spodoptera frugiperda in China. However, the mechanisms underlying how C. ruficrus locates its target pest remain unclear. In this study, we analyzed the expression patterns of 18 CrufOBPs across different developmental stages of C. ruficrus, and found that CrufOBP1 exhibited consistent and high expression levels in female adults. CrufOBP1 transcript was predominantly localized in sensilla placodea and sensilla trichodea on the antennae. Additionally, we confirmed the binding properties of CrufOBP1 protein to various cuticular compounds of S. frugiperda larvae. Subsequent electroantennogram and behavioral assays revealed that 1-(2-hydroxy-5-methylphenyl)-ethanone attracted female C. ruficrus, consequently increased the parasitism rate. However, upon silencing CrufOBP1, females exhibited reduced attraction towards 1-(2-hydroxy-5-methylphenyl)-ethanone, indicating the crucial role of CrufOBP1 in the chemoreception of C. ruficrus. These findings shed light on the kairomone-based mechanism employed by C. ruficrus to locate S. frugiperda larvae and hold a promise for the development of environmentally friendly pest management strategies.

The heat shock response in Polistes spp. brood from differing climates following heat stress.

Temperature is a crucial factor in many physiological processes, especially in small ectotherms whose body temperature is highly influenced by ambient temperature. Polistes (paper wasps) is a genus of primitively eusocial wasps found in widely varying thermal environments throughout the world. Paper wasps construct open-faced combs in which the brood is exposed to varying ambient temperatures. The Heat Shock Response is a physiological mechanism that has been shown to help cope with thermal stress. We investigated the expression of heat shock proteins in different life stages of three species of Polistes from different climates with the aim of deducing adaptive patterns. This was done by assaying heat shock protein (hsp70, hsp83, hsc70) expression during control conditions (25 °C) or a heat insult (35 or 45 °C) in individuals collected from natural populations in Alpine, Temperate, or Mediterranean climates. Basal expression of hsc70 and hsp83 was found to be high, while hsp70 and hsp83 expression was found to be highly responsive to severe heat stress. As expression levels varied based on species, geographical origin, and life stage as well as between heat shock proteins, the Heat Shock Response of Polistes was found to be complex. The results suggest that adaptive utilization of the heat shock response contributes to the ability of Polistes spp. to inhabit widely different thermal environments.

Modelling suggests Wolbachia-induced cytoplasmic incompatibility in oak gall wasps with cyclical parthenogenesis.

Oak gall wasps typically exhibit a life cycle with one sexual and one asexual generation each year. These wasps can carry various endosymbionts, one of which is the maternally inherited bacterium Wolbachia that can induce several reproductive manipulations on its host. Cytoplasmic incompatibility (CI) has been described as the most prominent of these manipulations. CI leads to embryonic mortality in the hosts' offspring when infected males mate with either uninfected females or with females that harbour different Wolbachia strains. It has been hypothesized that Wolbachia can induce CI in oak gall wasps. To address this hypothesis, we derived a mathematical model to investigate the spread of a bacterial infection in naive populations and to determine the plausibility of CI occurrence. To validate our model, we used published data from Wolbachia-infected Belonocnema kinseyi populations in two approaches. Our first approach uses measurements of infection frequencies and maternal transmission in the sexual generation. For the second approach, we extended the model to compare predictions to estimates of mtDNA-haplotypes, which, like Wolbachia, are maternally inherited, and can therefore be associated with the infection. Both approaches indicate that CI is present in these populations. Our model can be generalized to investigate the occurrence of CI not only for oak gall wasps but also for other species.

Hereditary nature of death-feigning frequency in a parasitoid wasp Heterospilus prosopidis using sib analysis.

Death feigning, a state of immobility observed in many animals in response to external stimuli, is an anti-predator behaviour. Although previous studies showed that death-feigning behaviours are quantitative genetic traits, the knowledge of the heritable basis of death-feigning behaviour is lacking. To investigate the heritable basis of death-feigning behaviour, we used 3 laboratory strains of a braconid parasitoid wasp, Heterospilus prosopidis. The heritable basis using half-sib analysis, and the effects of different geographical backgrounds, rearing conditions in the laboratory, and host age were evaluated. The results of the half-sib analysis showed that the frequency of death feigning varied among sires, suggesting a certain extent of additive genetic variance. Also, the frequency of death feigning varied between geographical backgrounds and among strains. Death-feigning frequency was not affected by the age of the host. Our findings highlight the importance of genetic factors underlying the basis of the death-feigning behaviour and provide support for the genetic alterations of traits from the perspective of evolution in various animal species.