Potential Insecticidal Effect of a Wasp (Polistes dominulus) and a Bee (Apis mellifera) Venoms in Controlling Spodoptera littoralis

Cotton leaf worm, Spodoptera littoralis, is considered one of the most common arthropod pests that contribute to crop devastation of cotton. Previously, agricultural pests were controlled through the application of chemical insecticides. However, insecticide-resistant insect populations emergence, as well as increasing concerns about the environmental and human health risks. Venomous animals introduce valuable sources of bioactive compounds which are employed for defence. Some of these toxins have high phyletic specificity, making them appropriate for use in IPM programs. This study aims to test the insecticidal effects of Polistes dominulus and Apis mellifera venoms. Crude venoms were examined for their insecticidal effect against cotton leaf worms by four different application methods including: leaf dipping, integument dropping, spraying, and injection. The data demonstrated a strong response to purified (Polistes dominulus) venom at an initial time than that of honey bee (Apis mellifera) which increases response with increasing the dose and the time interval. A dosage of 0.015 - 0.16 ml of both venoms had notably varied in LD50 values on Spodoptera littoralis that showed higher wasp venom toxicity. Cotton leaf worms showed more susceptibility and mortality to the Polistes sp. venom than that of honey bees.

Social buffer or avoidance depends on the similarity of stress between queen ants

The association of unrelated ant queens(pleometrosis)is supposed to improve nest foundation and competitiveness under environmental stress,but its evolutionary maintenance is difficult to explain because only one of the queens survives after nest foundation.My aim was to test the potential effect of queen association as a social buffer,that is,as a mechanism reducing stress and improving fitness due to the benefits of social contact.I analyzed the survival,fecundity,and behavior of isolated and paired Lasius flavus queens exposed and not exposed to stressors(disturbing environmental conditions).I found no difference in survivorship between isolated and paired queens or between stressed and unstressed isolated queens.Groups in which 1 or 2 paired queens were stressed showed higher mortality.Unstressed queens died similarly to their stressed nestmates,suggesting stress transmission.A trend suggested that paired queens produced eggs more quickly,but eggs were produced similarly between isolated and paired queens.Social avoidance was observed in groups with 1 stressed and 1 unstressed queen.However,the groups with 2 stressed queens showed the expected behaviors according to social buffering:lower mobility and more interindividual inspection.My findings suggest the synergistic effect of pleometrosis and stress and the dependence of stress level similarity between nestmates on social buffering or rejection on ant queens.

Juvenile hormone induces reproduction via miR-1175-3p in the red imported fire ant, Solenopsis invicta

Juvenile hormone(JH)acts in the regulation of caste differentiation between queens and workers(i.e.,with or without reproductive capacity)during vitellin synthesis and oogenesis in social insects.However,the regulatory mechanisms have not yet been elucidated.Here,we identified a highly expressed microRNA(miRNA),miR-1175-3p,in the red imported fire ant,Solenopsis invicta.We found that miR-1175-3p is prominently present in the fat bodies and ovaries of workers.Furthermore,miR-1175-3p interacts with its target gene,broad-complex core(Br-C),in the fat bodies.By utilizing miR-1175-3p agomir,we successfully suppressed the expression of the Br-C protein in queens,resulting in reduced vitellogenin expression,fewer eggs,and poorly developed ovaries.Conversely,decreasing miR-1175-3p levels led to the increased expression of Br-C and vitellogenin in workers,triggering the“re-development”of the ovaries.Moreover,when queens were fed with JH,the expression of miR-1175-3p decreased,whereas the expression of vitellogenin-2 and vitellogenin-3 increased.Notably,the suppression of fertility in queens caused by treatment with agomir miR-1175-3p was completely rescued by the increased vitellogenin expression induced by being fed with JH.These results suggest the critical role of miR-1175-3p in JH-regulated reproduction,shedding light on the molecular mechanism underlying miRNA-mediated fecundity in social insects and providing a novel strategy for managing S.invicta.

Gustatory responsiveness in Vespula germanica workers:exploring the interplay between sensory perception and task specialization

Workers'task specialization and division of labor are critical features of social insects'ecological success.It has been proposed that the division of labor relies on response threshold models:individuals varying their sensitivity(and responsiveness)to biologically relevant stimuli and performing a specific task when a stimulus exceeds an internal threshold.In this work,we study carbohydrate and protein responsiveness and their relation to worker task specialization in Vespula germanica,an invasive social wasp.The sucrose and peptone responsiveness of two different subcastes,preforagers and foragers,was determined by stimulating the antenna of the wasps with increasing concentrations of the solution and quantifying whether each concentration elicited a licking response.We studied responsiveness in five different ways:(1)response threshold,(2)concentration 50(concentration to which at least 50%of wasps responded),(3)maximum response,(4)mean scores and(5)median scores.Our results suggest that V germanica foragers are more sensitive to sucrose(lower thresholds)than preforager workers.However,we found no differences for peptone thresholds(i.e.,a protein resource).Nonetheless,this is the first study to investigate response thresholds for protein resources.The intercaste variation in sucrose responsiveness shown in our work contributes to the existing knowledge about response threshold theory as a mechanism for task specialization observed in V germanica.

Flexible foraging decisions made by workers of the social wasp Vespula germanica (Hymenoptera: Vespidae) in response to different resources: influence of ontogenetic shifts and colony feedback

Decisions made by foraging animals conform a complex process based on the integration of information from multiple external environmental stimuli and internal physiological signals,which in turn are modulated by individual experience and a detection threshold of each individual.For social insects in which foraging is limited to given age subcastes,individual foraging decisions may also be affected by ontogenetic shifts and colony requirements.We studied the short-term changes in foraging preferences of the generalist wasp Vespula germanica,focusing on whether the individual response to different resources could be influenced by the ontogenetic shifts and/or by social interaction with nestmates.We carried both laboratory and field experiments to confront worker wasps to a short-term resource switch between either protein or carbohydrate-based foods.We tested the response of(1)Preforager workers(no foraging experience nor interaction with other wasps),(2)Forager workers(experience in foraging and no colony feedback),and(3)Wild forager workers(foraging naturally and exposed to free interactions with nestmates).We evaluated the maxilla-labium extension response(MaLER)for laboratory assays or the landing response for field assays.We observed that for wasps deprived of colony feedback(either preforagers or foragers),the protein-rich foods acceptance threshold increased(and thus a lower level of foraging on that item was observed)if they had foraged on carbohydrates previously,whereas carbohydrates were accepted in all assays.However,wasps immersed in a natural foraging context did accept protein foods regardless of their first foraging experience and reduced the carbohydrates collected when trained on protein foods.We provide evidence that short-term changes in foraging preferences depend on the type of resource foraged and on the social interactions,but not on ontogenetic shifts.

The value of spatial experience and group size for ant colonies in direct competition

Animals often search for food more efficiently with experience.However,the contribution of experience toforaging success under direct competition has rarelybeen examined.Here we used colonies of an individually foraging desert ant to investigate the value of spatial experience.First,we trained worker groups of equal numbers to solve either a complex or a simple maze.We then tested pairs of both groups against one another in reaching a food reward.This task required solving the same complex maze that one of the groups had been trained in,to determine which group would exploit better the food reward.The worker groups previously trained in the complex mazes reached the food reward faster and more of these workers fed on the food than those trained in simple mazes,but only in the intermediate size group.To determine the relative importance of group size versus spatial experience in exploiting food patches,we then tested smaller trained worker groups against larger untrained ones.The larger groups outcompeted the smaller ones,despite the latter's advantage of spatial experience.The contribution of spatial experience,as found here,appears to be small,and depends on group size:an advantage of a few workers of the untrained group over the trained group negates its benefits.

Age and ovarian development are related to worker personality and task allocation in the ant Leptothorax acervorum

In social insects, workers of different morphological castes and age are known to act differently. Yet, it is unclear how body size and ovarian development influence worker personalities （i.e. consistent behavioral variation） and task allocation in similar aged ant workers of monomorphic species. Behavioral variation is thought to be a key element of division of labor, but few studies have linked worker personality to task allocation. We investigated individual behavior in Leptothorax acervorum ant workers at two time points during the first three months of their life and in two different settings. We observed worker behavior in the nest （i.e. task allocation） and in standardized aggression, exploration and brood care experiments （i.e. personality） and found behavioral repeatability in foraging and exploration. Further, workers acted consistently across settings： workers with a more ag gressive and exploratory personality type were more active in the nest. Moreover, ovarian development was associated with worker personality and task allocation： older workers with welldeveloped ovaries foraged less, but were more aggressive and exploratory. In accordance with the typical agepolyethism of social insects, workers became more active and foraged more as they grew older. Consequently, our study suggests that task allocation in Leptothorax acervorum is not only influenced by ovari an development and age, but moreover by the personalities of its workers .

The ecological consequences of temperament in spiders

Ecological and evolutionary studies on spiders have been featured prominently throughout the contemporary behavio- ral syndromes movement. Here we review the behavioral syndromes literature devoted to spiders, and identify some ways in which behavioral syndromes can impact the function of spiders in ecological communities. We further highlight three general themes within the behavioral syndromes literature for which spiders have served as front running model systems： （1） how trait correlations beget performance trade-offs, （2） the influence that behavioral trait variants have on interspecific interactions and （3） mechanisms that aid in maintaining behavioral variation within-and among-populations. Research on behavioral syndromes con-tinues to grow at an impressive rate, and we feel the success of behavioral syndromes studies in spiders bodes well for their con-tinued prominence.

Independent variations in genome-wide expression, alternative splicing, and DNA methylation in brain tissues among castes of the buff-tailed bumblebee, Bombus terrestris

Caste differentiation in social hymenopterans is an intriguing example of phenotypic plasticity. However, the co-ordination among gene regulatory factors to mediate caste differentiation remains inconclusive. In this study, we determined the role of gene regulation and related epigenetic processes in pre-imaginal caste differentiation in the primitively eusocial bumblebee Bombus terrestris. By combining RNA-Seq data from Illumina and Pac Bio and accurately quantifying methylation at whole-genomic base pair resolution, we found that queens, workers, and drones mainly differentiate in gene expression but not in alternative splicing and DNA methylation. Gynes are the most distinct with the lowest global level of whole-genomic methylation and with the largest number of caste-specific transcripts and alternative splicing events. By contrast, workers exhibit few uniquely expressed or alternatively spliced genes. Moreover, several genes involved in hormone and neurotransmitter metabolism are related to caste differentiation, whereas several neuropeptides are linked with sex differentiation. Despite little genome-wide association among differential gene expression, splicing, and differential DNA methylation, the overlapped gene ontology(GO) terms point to nutrition-related activity. Therefore, variations in gene regulation correlate with the behavioral differences among castes and highlight the specialization of toolkit genes in bumblebee gynes at the beginning of the adult stage.

Recognition of nestmate eggs in the ant Formicafusca is based on queen derived cues

Inclusive fitness benefits depend on recognizing the right individuals to interact with. Social insect nests protect themselves from non-kin intruders through nestmate recognition based on chemical cues. The recognition cues on adult individu- als are from a mixture of genetic and environmental sources, but the ontogeny and use of recognition cues on eggs has not been previously assessed. We studied recognition by workers of eggs that were either nestmates or non-nestmates, and the ontogeny of recognition cues on eggs in the ant Formica fusca, a species with precise egg recognition abilities. Workers were able to dis- criminate among freshly laid eggs with no nest derived cues on them, and the egg surface chemicals varied among nests in these eggs, suggesting that queen derived cues are used in nestmate recognition. The results are discussed in the light of their implica- tions on deceptive social parasite strategies and within colony conflicts

Polistes metricus queens exhibit personality variation and behavioral syndromes

Consistent differences in behavior between individuals, otherwise known as animal personalities, have become a staple in behavioral ecology due to their ability to explain a wide range of phenomena. Social organisms are especially serviceable to animal personality techniques because they can be used to explore behavioral variation at both the individual and group level. Despite the suc- cess of personality research in social organisms generally, and social Hymenoptera in particular, social wasps （Vespidae） have received little to no attention in the personality literature. In the pre- sent study, we test Polistes metricus （Vespidae; Polistinae） paper wasp queens for the presence of repeatable variation in, and correlations （＂behavioral syndromes＂） between, several commonly used personality metrics： boldness, aggressiveness, exploration, and activity. Our results indicate that P. metricus queens exhibit personalities for all measured traits and correlations between differ- ent behavioral measures. Given that paper wasps have served as a model organism for a wide range of phenomena such as kin selection, dominance hierarchies, mate choice, facial recognition, social parasitism, and chemical recognition, we hope that our results will motivate researchers to explore whether, or to what degree, queen personality is important in their research programs.

Dispersal behavior of yellowjacket （Vespula germanica） queens

Understanding the factors that affect animal dispersal behavior is important from both fi.mdamental and applied perspectives. Dispersal can have clear evolutionary and ecological consequences, but for normative insect pests, dispersal capacity can also help to explain invasion success. Vespula germanica is a social wasp that, in the last century, has successfully invaded several regions of the world, showing one of the highest spread rates reported for a nonnative insect. In contrast with nonsocial wasps, in social species, queens are responsible for population redistribution and spread, as workers are sterile. For V. germanica, it has been observed that queen flight is limited to 2 distinct periods： early autumn, when new queens leave the nest to mate and find sheltered places in which to hibernate, and spring when new colonies are founded. Our aim was to study the flight behavior of V. germanica queens by focusing on the different periods in which dispersal occurs, characterizing as well the potential contribution of queen flight （i.e., distance） to the observed geographical spread. Our results suggest that the distances flown by nonover- wintered queens is greater than that flown by overwintered individuals, suggesting that the main queen dispersal events would occur before queens enter hibernation. This could relate to a behavioral trait of the queens to avoid the inbreeding with related drones. Additionally, given the short distances flown and remarkable geographical spread observed, we provide evidence showing that queen dispersal by flight is likely to contribute proportionately less to population spread than human-aided factors.

Sperm traits differ between winged and wingless males of the ant Cardiocondyla obscurior

Size and shape of sperm cells vary tremendously throughout the animal kingdom.The adaptive significance of this variation is not fully understood.In addition to sperm-female interactions and the environmental condi­tions,the risk of sperm competition might affect number,morphology and other“quality”traits of sperm.In the male-diphenic ant Cardiocondyla obscurior,winged sneaker males have limited sperm number,because their testes degenerate shortly after adult emergence,as is typical for males of social Hymenoptera.In contrast,wing­less fighter males continuously replenish their sperm supply due to their exceptional lifelong spermatogene­sis.While winged males usually have to compete with several other winged males for virgin queens,wingless males are able to monopolize queens by killing all other rivals.Hence,this presents a unique system to inves­tigate how alternative reproductive tactics and associated physiology affect sperm morphology and viability.We found that sperm-limited males invest into sperm number instead of sperm size.Variance in sperm length is smaller in winged males,probably reflecting that they have to compete with several other males.Finally,sperm viability is equally high in both male phenotypes.