Pre-adult Development Research Articles

Effects of continuous and transgenerational rearing in peanut leaves on the performance and enzyme activity of Spodoptera frugiperda (Lepidoptera: Noctuidae).

The invasive fall armyworm (FAW), Spodoptera frugiperda, is a polyphagous pest that significantly threatens crops worldwide. FAW may undergo adaptation, enhancing its ability to infect specific plant hosts. However, there is limited knowledge on this topic. After 8 generations of constant rearing on peanut leaves, the performance and enzyme activities of FAW were investigated in this study. Compared to FAW fed on the peanut cultivars 'Fuhua 8' and 'Quanhonghua 1' for 2 generations, those grown on leaves for 5 to 8 generations had significantly shorter pre-adult development times and total preoviposition periods. Fecundity also increased significantly, resulting in an overall improvement in population fitness as measured by demographic parameters. However, the F2 generation of FAW fed on corn leaves outperformed the F8 generation of FAW fed on peanut leaves. In the F2 generation, the FAW peanut population exhibited 30-55% supernumerary larval molts, which decreased substantially in the F5 and F8 generations. Notably, supernumerary larval molts displayed pupation and emergence rates comparable to normal larvae, regardless of the peanut cultivar or rearing generation. The activities of lipase and acetylcholinesterase increased significantly from the F2 to F8 generations, showing substantial negative and positive correlations with larval development time and fecundity, respectively. In conclusion, FAW demonstrated inferior performance on peanut leaves compared to corn leaves, despite its performance was significantly improved after 5 to 8 generations of acclimation. These results suggest that corn will continue to be the primary target crop for FAW in China.

Insufficient and excessive Ca2+ intake negatively impact the life history performance and disrupt the hemolymph metabolism of Spodoptera litura

Calcium ions (Ca2+), essential as second messengers in all cells, play a pivotal role as micronutrients in insects. However, few studies have explored the effects of both insufficient and excessive Ca2+ intake on life history performance and population parameters. This study examines the impact of varying Ca2+ intake levels—insufficient (0 mg/kg), appropriate (100 mg/kg), and excessive (250 mg/kg)—on the life history performance and population parameters of Spodoptera litura using two-sex life tables. Insufficient and excessive Ca2+ intakes significantly extended the preadult development period and decreased the preadult survival rates of S. litura, compared to those on an appropriate Ca2+ intake. The population parameters (Intrinsic rate of increase (r), Finite rate of increase (λ), and Net reproductive rate (R0)) of S. litura on a 100 mg/kg diet (r = 0.1364, λ = 1.1462, R0 = 390) were significantly higher than those on a 0 mg/kg diet (r = 0.1091, λ = 1.1153, R0 = 130.52). Additionally, untargeted metabolomics analysis revealed that inappropriate Ca2+ levels (either insufficient or excessive) triggered significant up-regulation of 71.1 % and 92.8 % of the metabolites in the hemolymph, respectively, compared to the appropriate Ca2+ intake. Notably, disruptions in metabolite balance affected critical components such as melatonin and melanin within the tryptophan and tyrosine metabolism pathways. These findings underscore that both insufficient and excessive Ca2+ intakes adversely affect the life history performance and disrupt hemolymph metabolic balance in S. litura.

A mountain pine beetle (Coleoptera: Curculionidae) adult development rate model confirms evolved geographic differences.

Insects live in a wide range of thermal environments and have evolved species- and location-specific physiological processes for survival in hot and cold extremes. Thermally driven dormancy strategies, development rates and thresholds are important for synchronizing cohorts within a population and to local climates and often vary among populations within a species. Mountain pine beetle (MPB), Dendroctonus ponderosae Hopkins (Coleoptera: Curculionidae, Scolytinae),is a widely distributed forest insect native to North America with clinal genetic differentiation in thermally dependent traits. MPB development occurs in Pinus phloem beneath the bark, and its cryptic habitat makes experimentation difficult, particularly for the adult stage. We describe a novel method for modeling MPB adult development following pupation and terminating in emergence from a brood tree. We focus on an Arizona (southern) MPB population with previously described preadult development rates. Field-observed tree attack, adult emergence, and phloem temperature data are combined in a parameterized cohort model and candidate rate curves are evaluated to describe adult emergence timing. Model competition indicates that the Brière rate curve provided the best fit to field data and performed well under cross-validation. Results confirm that the development of Arizona MPB adults is slower than the previously described development rate of more northern Utah adults. Using the estimated adult rate curve in a scenario of increasing mean temperatures, we show that the timing of second-generation adult emergence in the same year would result in cold-intolerant lifestages during winter, limiting the success of bivoltine populations.

The influence of photoperiod on development and population growth performance of the Phytoseiulus persimilis fed on Tetranychus urticae

ABSTRACT Environmental factors, such as photoperiod, can play an important role in the development of mites. The influence of photoperiod (L:D = 4:20, 8:16, 12:12, 16:8 and 20:4) on the development and population parameters of the predatory mite, Phytoseiulus persimilis Athias-Henriot fed on two-spotted spider mite, Tetranychus urticae Koch was examined under laboratory conditions. Pre-adult development decreased with increasing photoperiod until 12 h, after which the development period progressively increased. Longevity of both sexes demonstrated significant differences throughout photoperiods, with the longest at 20:4 L:D and the shortest at 8:16 L:D. The highest value of mean total fecundity was 13.62 egg/female at 12:12 L:D photoperiod. The net reproductive rate (R 0), the intrinsic rate of increase (r) and the finite rate of increase (λ), showed the highest value at 12:12 L:D. The R 0, r and λ for P. persimilis increased with increasing photoperiod from 4:20 to 12:12 L:D, but decreased sharply at the 16:8 and 20:4 L:D treatments. Our findings indicate that photoperiod has a significant role in advancing the rate of development, survival rate, and reproduction for commercial production of P. persimilis, with a 12:12 photoperiod length recognized as the ideal period for commercial production in culture.

Dual stressors of infection and warming can destabilize host microbiomes.

Climate change is causing extreme heating events and intensifying infectious disease outbreaks. Animals harbour microbial communities, which are vital for their survival and fitness under stressful conditions. Understanding how microbiome structures change in response to infection and warming may be important for forecasting host performance under global change. Here, we evaluated alterations in the microbiomes of several wild Caenorhabditis elegans isolates spanning a range of latitudes, upon warming temperatures and infection by the parasite Leucobacter musarum. Using 16S rRNA sequencing, we found that microbiome diversity decreased, and dispersion increased over time, with the former being more prominent in uninfected adults and the latter aggravated by infection. Infection reduced dominance of specific microbial taxa, and increased microbiome dispersion, indicating destabilizing effects on host microbial communities. Exposing infected hosts to warming did not have an additive destabilizing effect on their microbiomes. Moreover, warming during pre-adult development alleviated the destabilizing effects of infection on host microbiomes. These results revealed an opposing interaction between biotic and abiotic factors on microbiome structure. Lastly, we showed that increased microbiome dispersion might be associated with decreased variability in microbial species interaction strength. Overall, these findings improve our understanding of animal microbiome dynamics amidst concurrent climate change and epidemics. This article is part of the theme issue 'Sculpting the microbiome: how host factors determine and respond to microbial colonization'.

Diet-induced plasticity of life-history traits and gene expression in outbred Drosophila melanogaster population.

Food is fundamental for the survival of organisms, governing growth, maintenance, and reproduction through the provision of essential macronutrients. However, access to food with optimum macronutrient composition, which will maximize the evolutionary fitness of an organism, is not always guaranteed. This leads to dietary mismatches with potential impacts on organismal performance. To understand the consequences of such dietary mismatches, we examined the effects of isocaloric diets varying in macronutrient composition on eight key organismal traits spanning across the lifespan of a large outbred Drosophila melanogaster population (n ~ 2500). Our findings reveal that carbohydrate-reduced isocaloric diets correlates to accelerated pre-adult development and boosts reproductive output without impacting pre-adult viability and body size. Conversely, an elevated dietary carbohydrate content correlated to reduced lifespan in flies, evidenced by accelerated functional senescence including compromised locomotor activity and deteriorating gut integrity. Furthermore, transcriptomic analysis indicated a substantial difference in gene regulatory landscapes between flies subject to high-carbohydrate versus high-protein diet, with elevated protein levels indicating transcriptomes primed for reduced synthesis of fatty acids. Taken together, our study helps advance our understanding of the effect of macronutrient composition on life history traits and their interrelations, offering critical insights into potential adaptive strategies that organisms might adopt against the continual dietary imbalances prevalent in the rapidly evolving environment.

Effects of visible light wavelength on development and demographic parameters of Phytoseiulus persimilis (Acari: Phytoseiidae)

Environmental factors, such as the wavelength of light, can have a crucial impact on mite development. Little is, however, known about the effect of visible light quality on demographic parameters of Phytoseiidae. We therefore conducted series of laboratory experiments in which development and reproduction of Phytoseiulus persimilis Athias-Henriot feeding on Tetranychus urticae Koch eggs was investigated under various light conditions (white, blue, green, yellow, and red light). The results revealed that different light wavelengths influenced each developmental stage, with the green light conditions promoting longest pre-adult development. The longevity of both male and female mites varied significantly across light wavelengths, with the shortest lifespan observed under red light. The highest mean total fecundity, 16 eggs per female, was observed under white light conditions. Population parameters (R0, r, and λ) were also highest under white light and decreased with increasing light wavelength. These findings suggest that light wavelength plays a significant role in development, survival, and reproduction of the predatory mite, with white light being identified as providing the best light conditions for commercial production of P. persimilis.

The Lethal and Sublethal Effects of Lambda-Cyhalothrin and Emamectin Benzoate on the Soybean Pest Riptortus pedestris (Fabricius).

Riptortus pedestris (Fabricius, 1775) (Hemiptera: Alydidae) is a major soybean pest in East Asia that can cause soybean staygreen syndrome. To date, no insecticides have been registered for the control of R. pedestris in China, and these insects are primarily controlled in the field through the application of broad-spectrum insecticides including lambda-cyhalothrin (LCT) and emamectin benzoate (EMB). Here, the lethal and sublethal effects of LCT and EMB on R. pedestris were comprehensively evaluated. LCT and EMB were both found to exhibit high levels of toxicity and concentration-dependent repellent effects for R. pedestris. The exposure of third instar nymphs from the F0 generation to LC30 concentrations of LCT and EMB resulted in a significant increase in the duration of nymph development and adult pre-oviposition period (APOP), together with reductions in fifth instar nymph and adult body weight, longevity, oviposition days, fecundity, vitellarium length, lateral oviduct diameter, and vitellogenin (Vg) gene expression as compared to control treatment. Strikingly, these suppressive effects were transmitted to the F1 generation, which similarly experienced the prolongation of preadult development and the preoviposition period (TPOP). Relative to control-treated populations, the F1 generation for these insecticide-treated groups also exhibited significant decreases in population parameter values. Overall, these data offer new insight into the impact that LCT and EMB treatment can have on R. pedestris, providing a valuable foundation for the application of these pesticides in the context of integrated pest management strategies aimed at soybean crop preservation.

Side effects of insecticides alone or in a mixture with acaricide on life history traits and demographic parameters of Brevipalpus yothersi

Brevipalpus yothersi is an important pest to citrus crop due to its ability to transmit the virus that causes citrus leprosis. The exposure of target and non-target organisms to different pesticides is a reality in field conditions. For successful management, it is essential to determine the effects of citrus commonly used pesticides on leprosis mites to determine how pesticides can interfere with the leprosis mite population. Therefore, this study aimed to evaluate the impact of insecticides, alone or associated with spirodiclofen, on B. yothersi life history traits and demographic parameters under laboratory and greenhouse conditions. Results suggest that cypermethrin and imidacloprid, both alone and in a mixture with spirodiclofen, phosmet in a mix with spirodiclofen and spirodiclofen alone did not interfere significantly in the fecundity and fertility of B. yothersi in laboratory conditions. In the same condition, only phosmet at 15.6, 125.0, and 250.0 mg.L-1 reduced the fecundity of the mites. Brevipalpus yothersi population varied with the insecticide and mixture type in the greenhouse condition. Most insecticides and acaricide, alone or in a mixture, decreased pre-adult development, whereas female adult longevity was similar to control. Spirodiclofen combined with phosmet and imidacloprid decreased female adult longevity. Only spirodiclofen in a mixture with cypermethrin and phosmet alone did not interfere significantly with the intrinsic rate of population increase. The other insecticides and mixtures reduced that parameter. The mean time of one mite generation was decreased when the mites were exposed to all insecticides and acaricide combinations, spirodiclofen and phosmet alone. Therefore, cypermethrin, phosmet, imidacloprid, and spirodiclofen, alone or in a mixture, negatively impacted the development time and demographic parameters of B. yothersi.

New application of ATR-FTIR spectroscopy for postmortem interval estimation based on puparia of the sarcosaprophagous fly Chrysomya megacephala (Diptera: Calliphoridae)

Postmortem interval (PMI) estimation remains a challenge in forensic science due to the lack of efficient methods. In recent years, the preadult development of sarcosaprophagous flies has been recognized as a reliable method to estimate the minimum postmortem interval (PMImin). However, this method may fail once the PMI exceeds the duration of preadult development (i.e. after eclosion), leaving puparia of sarcosaprophagous flies as the only evidence for the estimation of the PMI at the crime scene. Fourier transform infrared (FTIR) spectroscopy with attenuated total reflectance (ATR) accessory was used in this study to collect comprehensive biochemical information from puparia of the sarcosaprophagous fly Chrysomya megacephala (Fabricius) (Diptera, Calliphoridae) at different time after eclosion (TAE). We established the partial least square (PLS) regression model using the acquired spectral dataset. The prediction results of the PLS regression model showed that R2CV of the internal cross-validation (calibration dataset) was 0.864 with RMSECV = 3.711 d and R2P of the prediction dataset was 0.909 with RMSEP = 3.045 d. The RMSEP/RMSECV value was 0.82 in our PLS regression model. Our results indicate that the TAE of puparia are highly predictable, which is valuable for the estimation of long-term PMImin.

The Invasive Caucasian Populations of the Brown Marmorated Stink Bug Halyomorpha halys (Hemiptera: Heteroptera: Pentatomidae) Rapidly Adapt Their Ecophysiological Traits to the Local Environmental Conditions

The ability to rapidly adapt to new environmental conditions is a crucial prerequisite for the wide-scale invasion of pests or intentional introduction of beneficial insects. A photoperiodically induced facultative winter diapause is an important adaptation ensuring synchronization of insect development and reproduction with the local seasonal dynamics of environmental factors. We conducted a laboratory study aimed to compare photoperiodic responses of two invasive Caucasian populations of the brown marmorated stink bug Halyomorpha halys (Hemiptera: Heteroptera: Pentatomidae), which recently invaded neighboring regions with subtropical (Sukhum, Abkhazia) and temperate (Abinsk, Russia) climates. Under the temperature of 25 °C and the near-critical photoperiods of L:D = 15:9 h and 15.5:8.5 h, the population from Abinsk showed a slower pre-adult development and a stronger tendency to enter winter adult (reproductive) diapause compared to the population from Sukhum. This finding agreed with the difference between the local dynamics of the autumnal temperature decrease. Similar adaptive interpopulation differences in the patterns of diapause-inducing responses are known in other insect species but our finding is distinguished by a very short adaptation time: H. halys was first recorded in Sukhum in 2015 and in Abinsk in 2018. Thus, the differences between the compared populations might have evolved over a relatively short span of several years.

Monochromatic visible lights modulate the timing of pre-adult developmental traits in Drosophila melanogaster.

Light exposure impacts several aspects of Drosophila development including the establishment of circadian rhythms, neuroendocrine regulation, life-history traits, etc. Introduction of artificial lights in the environment has caused almost all animals to develop ecological and physiological adaptations. White light which comprises different lights of differing wavelengths shortens the lifespan in fruit flies Drosophila melanogaster. The wavelength-specific effects of white light on Drosophila development remains poorly understood. In this study, we show that different wavelengths of white light differentially modulate Drosophila development in all its concomitant stages when maintained in a 12-h light: 12-h dark photoperiod. We observed that exposure to different monochromatic lights significantly alters larval behaviours such as feeding rate and phototaxis that influence pre-adult development. Larvae grown under shorter wavelengths of light experienced an altered feeding rate. Similarly, larvae were found to avoid shorter wavelengths of light but were highly attracted to the longer wavelengths of light. Most of the developmental processes were greatly accelerated under the green light regime while in other light regimes, the effects were highly varied. Interestingly, pre-adult survivorship remained unaltered across all light regimes but light exposure was found to show its impact on sex determination. Our study for the first time reveals how different wavelengths of white light modulate Drosophila development which in the future might help in developing non-invasive therapies and effective pest measures.

Heightened immune surveillance in Drosophila melanogaster populations selected for faster development and extended longevity

Maximization of life-history traits is under constraints due to both, limitations of resource acquisition and the restricted pathways of resource allocation. Drosophila melanogaster has served as an excellent model organism to not only unravel various trade-offs among life history traits but also numerous aspects of host immune response. Drosophila larvae are semi-aquatic that live, feed and excrete inside the food source-often over-ripe fruits and vegetables that are rich in both commensal and pathogenic microbiota that can impact the larval survival. In this study, we have used six populations of D. melanogaster, three of which are selected for faster pre-adult development and extended adult longevity, and their three ancestral controls, to explore the impact of selection on the basal immune activity in the larval stage. The larvae from selected populations had nearly significantly upregulated plasmatocyte density, significantly higher percent phagocytosis, phagocytic index and higher transcript levels of Tep3, eater and NimC1. Selected populations also had significantly upregulated crystal cell number along with higher transcript of PPO2. Out of seven tested AMPs level, Drosomycin was significantly upregulated in selected populations while Drosocin was significantly higher in control populations. ROS levels were comparable in the selected and control populations. Our results strongly suggest that enhanced basal immune activity during larval stage manages the faster development and could be responsible for comparable larval survival of selected and control populations.

Effects of Elevated CO2 on the Fitness Parameters of Individually- and Group-Reared Agasicles hygrophila (Coleoptera: Chrysomelidae).

Agasicles hygrophila Selman and Vogt (Coleoptera: Chrysomelidae) is a natural enemy of Alternanthera philoxeroides (Mart.) Griseb (Amaranthaceae: Alternanthera), a worldwide invasive weed. Elevated atmospheric CO2 concentrations may have significant impacts plants, herbivorous insects, and natural enemies. To assess the concurrent effect of elevated CO2 on the development time, fecundity, and population parameters of A. hygrophila, the age-stage, two-sex life table was used to understand the fitness and population parameters of individually-reared and group-reared A. hygrophila under elevated CO2 concentration. In individually-reared population, the development time of preadults, adult pre-oviposition period, and total pre-oviposition period of A. hygrophila in the elevated CO2 (eCO2, 750 ppm) treatment were shorter than those in the ambient CO2 (aCO2, 420 ppm) treatment. In group-reared population, the developmental time of preadults, female adult longevity, female proportion, adult pre-oviposition period, and total pre-oviposition period of A. hygrophila in eCO2 were longer than those in aCO2. Additionally, in both individually-reared and group-reared population, fecundity and oviposition days of A. hygrophila in eCO2 were higher than those in aCO2, and a higher intrinsic rate of increase, finite rate of increase, and the net reproductive rate of A. hygrophila were observed at eCO2. Moreover, shorter preadult development time, adult pre-oviposition period, total pre-oviposition period, male adult longevity, and higher fecundity were found in group-reared cohort at both aCO2 and eCO2. The results indicates that elevated CO2 has effects on the growth and reproduction of A. hygrophila, and the population growth rate of group-reared was faster and produced more offspring.

Meet Me Halfway: Will Photoperiodic Responses of Interpopulation Hybrids of the Brown Marmorated Stink Bug Halyomorpha halys (Hemiptera: Heteroptera: Pentatomidae) Promote or Constrain Subsequent Invasions?

Biological invasions often result from multiple invasion events. In the case of several subsequent invasive episodes, ‘newcomers’ are usually poorly adapted to local environmental conditions in contrast to the representatives of the already-established invasive population of the same species. Therefore, the mode of inheritance of life-history features determining the survival and performance of interpopulation hybrids is an important component of invasiveness. We investigated the mode of inheritance of the photoperiodic response in the brown marmorated stink bug, Halyomorpha halys, by crossing between the native population of South Korea and the invasive population of the Black Sea coast of Russia. The aim of this study was to predict the overwintering potential of the progeny from possible crosses between representatives of the native and invasive populations. The pre-adult development time and the incidence of winter adult diapause in the progeny of the interpopulation crosses were close to the average of the values recorded in ‘pure’ (unmixed) crosses. Female and male genotypes were equally important in the determination of these characters. Such a mode of inheritance is most likely determined by a polygenic control and would only partially promote subsequent invasion events from the native South Asian range of H. halys into Europe.

To Every Thing There Is a Season: Phenology and Photoperiodic Control of Seasonal Development in the Invasive Caucasian Population of the Brown Marmorated Stink Bug, Halyomorpha halys (Hemiptera: Heteroptera: Pentatomidae).

Simple SummaryThe brown marmorated stink bug originates in East Asia and recently invaded Europe and North America. It is considered a serious pest because it damages 300+ species of wild and cultivated crops. Studies on the seasonal development of local populations of invasive insects are important for monitoring damage and predicting their dispersion. We investigated the seasonal development of this pest in Sochi (Krasnodar Territory, Russia) from 2018 to 2021 by regular field sampling. The results suggest that the brown marmorated stink bug normally produces two generations per year in the studied region: the main period when overwintered females lay eggs occurs from June to July; the second period of egg-laying (by females of the new generation) occurs in August. Reproductively active adult bugs were recorded from the end of May to the beginning of September. Such seasonal activity correlates with day length: when days became shorter than the experimentally determined critical value (15.0–15.5 h), the proportion of females with fully developed reproductive organs sharply dropped to zero. The timing of the beginning of the winter dormancy observed under the natural conditions agrees with the predictions based on the results of the earlier conducted laboratory experiments.Studies on the phenology of local populations of invasive insects are necessary for monitoring and predicting their dispersion. We investigated the phenology of the brown marmorated stink bug, Halyomorpha halys, in the Sochi region (Krasnodar Territory, Russia) from 2018 to 2021 by regular field sampling and dissecting. The results of the sampling suggest that H. halys is at least partially bivoltine in the studied region: the main period of mass oviposition (by the overwintered females) occurs from June to July; the second, much shorter period of egg-laying (by females of the new, i.e., the first generation) occurs in August. Reproductively active individuals (i.e., females with developed ovaries and filled spermatheca and males with filled ectodermal sac) were recorded from the end of May to the beginning of September. Such a seasonal pattern correlated with day length: when the natural photoperiod decreased below the experimentally determined critical day length (15.0–15.5 h), the proportions of females with fully developed ovaries sharply dropped to zero. Both the rate of H. halys pre-adult development and the timing of the induction of winter adult diapause observed under natural conditions fully agreed with the earlier predictions that had been based on the results of laboratory experiments.

The effects of storage temperature, food, and humidity on survival and progeny of Neoseiulus bicaudus

AbstractNeoseiulus bicaudus Wainstein (Acari: Phytoseiidae) is a beneficial predatory mite to control spider mites. To evaluate the suitable storage conditions of N. bicaudus, the survival of adult females was observed under different combinations of low temperature (3, 6, 9, or 12°C), food (F) or no food (NF), and high (H) or low (L) humidity conditions for 7, 14, 21, 28, and 35 d. Predator mites’ longevity and survival time of 50% and 80% individuals (ST50,80) were measured and compared between treatments. After storage, female and male living mites were paired at 26°C. The progeny parameters were evaluated after storage. Results revealed that survival rate decreased as storage temperature decreased. At 3 and 6°C, fewer mites survived after 28 d. At 9°C, ~50% of the females survived in the FH treatment after 35 d. At 12°C, >80% survived 7–35 d in the FH treatment. Moreover, longevity and ST50,80 were significantly greater in the FH treatment than in the FL or NFH treatments at 3, 9, and 12°C. The highest longevity (48.6 ± 3.7 d) and ST50 (51.6 d) occurred at 12°C in the FH treatment. There was no effect on progeny hatching or survival rates when adults were stored at 9 or 12°C for 28 d. At 9°C, the total preadult development time was 4.20–5.25 d. At 12°C, the total development time was 4.87–4.93 d and there was no significant difference between the storage treatment and control group. These results demonstrated that N. bicaudus females can be successfully stored at 9°C for ~21 d and 12°C for ~28 d with little effect on adult survival or progeny parameters.

Population Parameters and Growth of Riptortus pedestris (Fabricius) (Hemiptera: Alydidae) under Fluctuating Temperature.

Simple SummaryThe bean bug, Riptortus pedestris, is a polyphagous species that is an important pest of soybean fields in Asian countries. In this study, we examined the effects of constant and fluctuating temperatures on the development and reproduction of R. pedestris. The effects of thermal conditions were assessed by constructing age-stage, two-sex life tables from a constant temperature of 24 °C and simulated fluctuating temperatures of 24 ± 4 °C, 24 ± 6 °C, and 24 ± 8 °C. At a constant temperature, a number of R. pedestris life table parameters differed from those under fluctuating temperatures. Although similar pre-adult development periods were recorded under constant and fluctuating temperatures, the periods of female longevity and oviposition periods under fluctuating temperatures were significantly longer than those at a constant temperature. Given that temperature is an important abiotic factor for forecasting the population dynamics of arthropods in nature, determining the effects of fluctuating temperatures will make a valuable contribution to predicting R. pedestris population growth.In this study, we determined the influence of fluctuating temperatures on the development and fecundity of the bean bug Riptortus pedestris (Fabricius) (Hemiptera: Alydidae) by collecting life table data for individuals exposed at a constant temperature (24 °C) and three fluctuating temperatures (24 ± 4 °C, 24 ± 6 °C, and 24 ± 8 °C). The raw life history data were analyzed using an age-stage, two-sex life table to take into account the viable development rate among individuals. Based on these analyses, the population projections enabled us to determine the stage structure and variability of population growth under different temperature treatments. Our results revealed shorter periods of immature development and a higher pre-adult survival rate at 24 ± 6 °C than under the other assessed temperature conditions. Furthermore, significant reductions in female longevity were recorded at 24 °C, whereas the fecundity, net reproductive rate, and intrinsic and finite rates of increase were highest at 24 ± 6 °C. These findings reveal that fluctuating temperatures have a positive influence on the life history traits of R. pedestris and indicate that observations made under constant temperatures may not explain sufficiently enough the temperature dependent biological performances of pests in the field.

Body size correlations with female aggression and physiology suggest pre-adult effects on caste in an independent-founding eusocial paper wasp (Mischocyttarus pallidipectus, Hymenoptera Vespidae)

Reproductive castes are a defining characteristic of eusocial insects. The developmental timing of reproductive caste differentiation is important to shaping individual opportunities for reproductive flexibility. Because hard-part body size (e.g., wing length) is fixed for insects upon adult emergence, morphology can be used to assess pre-adult effects on caste status. Differences in body size amongst adult colony mates may affect social competition for resources and reproductive status in caste-monomorphic species. Our goal was to use body size correlations with female behavior and physiology to test among three hypotheses for pre-emergent effects on female caste within colonies of Mischocyttarus pallidipectus paper wasps: (1) no size overlap between females with developed and undeveloped ovaries would indicate caste is likely determined during larval development; (2) size bias for reproductives with exceptions: caste could be biased during development, but post-emergence factors may play a role; (3) no size patterns: no morphological evidence for pre-adult caste biases. Within colonies, we found a significant difference in body size (wing length) between females with developed vs undeveloped ovaries: larger females were more likely to have developed ovaries. Additionally, larger females were more aggressive towards nestmates. However, there was considerable variation in body size effects on both ovary development and behavioral dominance: even some of the smallest-bodied females had developed ovaries and were socially aggressive. These data suggest factors during pre-adult development lead to morphological (size) differences, and that body size affects the outcome of adult interactions with implications for reproductive caste.

Evolution of reproductive traits have no apparent life-history associated cost in populations of Drosophila melanogaster selected for cold shock resistance

BackgroundIn insect species like Drosophila melanogaster, evolution of increased resistance or evolution of particular traits under specific environmental conditions can lead to energy trade-offs with other crucial life-history traits. Adaptation to cold stress can, in principle, involve modification of reproductive traits and physiological responses. Reproductive traits carry a substantial cost; and therefore, the evolution of reproductive traits in response to cold stress could potentially lead to trade-offs with other life-history traits. We have successfully selected replicate populations of Drosophila melanogaster for increased resistance to cold shock for over 33 generations. In these populations, the ability to recover from cold shock, mate, and lay fertile eggs 24 h post cold shock is under selection. These populations have evolved a suite of reproductive traits including increased egg viability, male mating ability, and siring ability post cold shock. These populations also show elevated mating rate both with and without cold shock. In the present study, we quantified a suite of life-history related traits in these populations to assess if evolution of cold shock resistance in these populations comes at a cost of other life-history traits.ResultsTo assess life-history cost, we measured egg viability, mating frequency, longevity, lifetime fecundity, adult mortality, larva to adult development time, larvae to adults survival, and body weight in the cold shock selected populations and their controls under two treatments (a) post cold chock and (b) without cold shock. Twenty-four hours post cold shock, the selected population had significantly higher egg viability and mating frequency compared to control populations indicating that they have higher cold shock resistance. Selected populations had significantly longer pre-adult development time compared to their control populations. Females from the selected populations had higher body weight compared to their control populations. However, we did not find any significant difference between the selected and control populations in longevity, lifetime fecundity, adult mortality, larvae to adults survival, and male body weight under the cold chock or no cold shock treatments.ConclusionsThese findings suggest that cold shock selected populations have evolved higher mating frequency and egg viability. However, there is no apparent life-history associated cost with the evolution of egg viability and reproductive performances under the cold stress condition.