Report of forensically relevant insects collected from pig and rabbit remains during two forensic entomology workshops in Eastern Massachusetts

Forensic entomology relies on known geographic ranges and seasonal presence of forensically relevant insects. In the Northeastern United States, there is no information on species in the region in early spring. Two forensic entomology workshops took place in April of 2023 and 2024 in Milton, Massachusetts. During this workshop, practitioners were trained in the appropriate collection and storage techniques prior to a practical experience including the collection of insects from pig and rabbit remains. All insects collected were identified down to family or species level. Across both years, Phormia regina (Meigen) (Diptera: Calliphoridae) was the fly consistently colonizing remains and was the oldest immature larvae in all instances. Calliphora vicina (Robineau-Desvoidy) (Diptera: Calliphoridae), Protophormia terraenovae (Robineau-Desvoidy) (Diptera: Calliphoridae), and Muscina stabulans (Fallén) (Diptera: Muscidae) were additional flies co-colonizing remains with P. regina. Other species were found as adults surrounding the remains that included other necrophagous fly species, beetles, and ants. Variation in insects collected between years likely due to high temperature variation. This documentation of species provides context to forensically related flies expected in Eastern Massachusetts and provides research directives in the region.

Cold tolerance and prediction of northern distribution of Histia rhodope (Lepidoptera: Zygaenidae) in China

Histia rhodope (Cramer) (Lepidoptera: Zygaenidae) is one of the most destructive defoliating pests of the landscape tree Bischofia polycarpa (Levl.) S in China and other Southeast Asian regions, posing a critical threat to urban landscapes and their ecological benefits. This pest has shown a trend of northward range shift in recent years in China, making it urgent to understand its potential distribution. This study investigated the cold tolerance of overwintering H. rhodope larvae from October 2022 to March 2023 and estimated their overwintering potential in China. The results showed that the supercooling points (SCP) differed significantly across months. The SCP tended to decrease as the ambient temperature dropped until January, after which it gradually increased until the end of winter. The highest monthly mean SCP was -7.5 ± 2.22°C (October 2022), while the lowest monthly mean SCP was -15.09 ± 2.61°C (January 2023). The mortality rate increased with longer exposure times and lower exposure temperatures but decreased as winter progressed. Moreover, 50% and 90% lethal temperature (Ltemp50 and Ltemp90) exhibited a similar trend, decreasing to a minimum in January 2023, which indicates increased cold tolerance during the colder months. Using Ltemp90 in January as the isotherm for its northern limit indicated that H. rhodope may be limited by low temperatures along the 40°N latitude. These results provide a basis for predicting the dispersal potential and possible geographic range of this pest in China.

Development of a Baltimore (MD) population of Calliphora vicina (Diptera: Calliphoridae) reared at several temperatures and estimations of developmental limits and thresholds

Developmental data for necrophagous Diptera are frequently used in medico-legal investigations to estimate portions of the postmortem interval and interpret periods of insect activity. These applications require baseline developmental data for local populations from geographic locations of interest. For the widely distributed blow fly Calliphora vicina Robineau-Desvoidy (Diptera: Calliphoridae), detailed developmental data does not exist for many locations in the mid-Atlantic region of the United States. This study examined development of C. vicina collected from a large, metropolitan city (Baltimore) in Maryland utilizing 11 ambient temperatures. The developmental threshold and thermal range of growth and tolerance were also estimated, as well as critical thermal minima and maxima based on thermal injury. For this population, linear growth was observed between 10°C and 25°C, whereas flies failed to complete development at temperatures below 7°C or above 28°C. Growth at low temperatures was not curvilinear, which contrasts with other developmental studies using C. vicina and other calliphorids. The lower developmental threshold was estimated to be 5.9°C and corresponds closely with experimental observations. The implications of these result in reference to phenotypic plasticity in populations of C. vicina and applications in forensic entomology are discussed.

Larval and adult diet affect phenotypic plasticity in thermal tolerance of the marula fly, Ceratitis cosyra (Walker) (Diptera: Tephritidae)

Introduction

Temperature fluctuations are important for the distribution and survival of insects. Rapid hardening, a type of phenotypic plasticity, is an adaptation that can help individuals better tolerate lethal temperatures because of earlier exposure to a sublethal but stressful temperature. Nutrition and sex are also known to influence a species ability to tolerate thermal stress. This study determined the effects of larval diet, adult diet, sex and hardening on the thermal tolerance of Ceratitis cosyra (Walker) (Diptera: Tephritidae) at lower and upper lethal temperatures.

Methods

Larvae were raised on either an 8% torula yeast (high) or a 1% torula yeast (low) larval diet and then introduced to one of three dietary regimes as adults for thermal tolerance and hardening assays: no adult diet, sugar only, or sugar and hydrolysed yeast diet. Flies of known weight were then either heat- or cold-hardened for 2 hours before being exposed to a potentially lethal high or low temperature, respectively.

Results

Both nutrition and hardening as well as their interaction affected C. cosyra tolerance of stressful temperatures. However, this interaction was dependent on the type of stress, with nutrient restriction and possible adult dietary compensation resulting in improved cold temperature resistance only.

Discussion

The ability of the insect to both compensate for a low protein larval diet and undergo rapid cold hardening after a brief exposure to sublethal cold temperatures even when both the larva and the subsequent adult fed on low protein diets indicates that C. cosyra have a better chance of survival in environments with extreme temperature variability, particularly at low temperatures. However, there appears to be limitations to the ability of C. cosyra to cold harden and the species may be more at risk from long term chronic effects than from any exposure to acute thermal stress.

The metabolism and role of free fatty acids in key physiological processes in insects of medical, veterinary and forensic importance

Insects are the most widespread group of organisms and more than one million species have been described. These animals have significant ecological functions, for example they are pollinators of many types of plants. However, they also have direct influence on human life in different manners. They have high medical and veterinary significance, stemming from their role as vectors of disease and infection of wounds and necrotic tissue; they are also plant pests, parasitoids and predators whose activities can influence agriculture. In addition, their use in medical treatments, such as maggot therapy of gangrene and wounds, has grown considerably. They also have many uses in forensic science to determine the minimum post-mortem interval and provide valuable information about the movement of the body, cause of the death, drug use, or poisoning. It has also been proposed that they may be used as model organisms to replace mammal systems in research. The present review describes the role of free fatty acids (FFAs) in key physiological processes in insects. By focusing on insects of medical, veterinary significance, we have limited our description of the physiological processes to those most important from the point of view of insect control; the study examines their effects on insect reproduction and resistance to the adverse effects of abiotic (low temperature) and biotic (pathogens) factors.

Differential Response of Leafminer Flies Liriomyza trifolii (Burgess) and Liriomyza sativae (Blanchard) to Rapid Cold Hardening

Simple Summary

Liriomyza trifolii (Burgess) and L. sativae (Blanchard) are closely-related, polyphagous leafminers that occur worldwide and presumably compete with each other. In this study, we evaluated the response of pupae and adults from both species to acute (2 h) cold exposures. The results were used to identify the lethal temperature for 80% of the population (LT80) for each species. In a separate set of experiments, insects were cooled to one of six nonlethal temperatures (0–5 °C) for 4 h and then cooled to the LT80 for 2 h to evaluate their rapid cold hardening (RCH) response. L. trifolii exhibited stronger cold tolerance than L. sativae; furthermore, the supercooling point of L. trifolii was significantly lower than that of L. sativae. RCH was induced in pupae of both species at a range of low temperatures (0–5 °C), and L. sativae pupae showed a more robust RCH response (e.g., lower supercooling pointand more durable RCH) than L. trifolii pupae. Our results indicate that subtle differences in RCH and basal cold tolerance impact the competitiveness of the two leafminers.

Abstract

Rapid cold hardening (RCH) is a rapid and critical adaption of insects to sudden temperature changes but is often overlooked or underestimated as a component of survival. Thus, interspecific comparisons of RCH are needed to predict how phenotypes will adapt to temperature variability. RCH not only enhances cold survival but also protects against non-lethal cold injury by preserving essential functions such as locomotion, reproduction, and energy balance. This study investigated the difference in basal cold tolerance and RCH capacity of L. trifolii and L. sativae. In both species, the cold tolerance of pupae was significantly enhanced after short-term exposure to moderately cold temperatures. The effect of RCH last for 4 h in L. sativae but only 2 h in L. trifolii. Interestingly, L. trifolii adults had a RCH response but L. sativae adults failed to acclimate. Short-term acclimation also lowered the supercooling point significantly in the pupae of both species. Based on these results, we propose a hypothesis that these differences will eventually affect their competition in the context of climate change. This study also provides the basis for future metabolomic and transcriptomic studies that may ultimately uncover the underlying mechanisms of RCH and interspecific competition between L. trifolii and L. sativae.

Thermal history of alfalfa leafcutting bees affects nesting and diapause incidence

Variable spring temperatures may expose developing insects to sublethal conditions, resulting in long-term consequences. The alfalfa leafcutting bee, Megachile rotundata, overwinters as a prepupa inside a brood cell, resuming development in spring. During these immobile stages of development, bees must tolerate unfavorable temperatures. In this study, we tested how exposure to low temperature stress during development affects subsequent reproduction and characteristics of the F1 generation. Developing male and female M. rotundata were exposed to either constant (6°C) or fluctuating (1 h day-1 at 20°C) low temperature stress for 1 week, during the pupal stage, to mimic a spring cold snap. Treated adults were marked and released into field cages, and reproductive output was compared with that of untreated control bees. Exposure to low temperatures during the pupal stage had mixed effects on reproduction and offspring characteristics. Females treated with fluctuating low temperatures were more likely to nest compared with control bees or those exposed to constant low temperature stress. Sublethal effects may have contributed to low nesting rates of bees exposed to constant low temperatures. Females from that group that were able to nest had fewer, larger offspring with high viability, suggesting a trade-off. Interestingly, offspring of bees exposed to fluctuating low temperatures were more likely to enter diapause, indicating that thermal history of parents, even during development, is an important factor in diapause determination.

Local thermal environment and warming influence supercooling and drive widespread shifts in the metabolome of diapausing Pieris rapae butterflies

Global climate change has the potential to negatively impact biological systems as organisms are exposed to novel temperature regimes. Increases in annual mean temperature have been accompanied by disproportionate rates of change in temperature across seasons, and winter is the season warming most rapidly. Yet, we know relatively little about how warming will alter the physiology of overwintering organisms. Here, we simulated future warming conditions by comparing diapausing Pieris rapae butterfly pupae collected from disparate thermal environments and by exposing P. rapae pupae to acute and chronic increases in temperature. First, we compared internal freezing temperatures (supercooling points) of diapausing pupae that were developed in common-garden conditions but whose parents were collected from northern Vermont, USA, or North Carolina, USA. Matching the warmer winter climate of North Carolina, North Carolina pupae had significantly higher supercooling points than Vermont pupae. Next, we measured the effects of acute and chronic warming exposure in Vermont pupae and found that warming induced higher supercooling points. We further characterized the effects of chronic warming by profiling the metabolomes of Vermont pupae via untargeted LC-MS metabolomics. Warming caused significant changes in abundance of hundreds of metabolites across the metabolome. Notably, there were warming-induced shifts in key biochemical pathways, such as pyruvate metabolism, fructose and mannose metabolism, and β-alanine metabolism, suggesting shifts in energy metabolism and cryoprotection. These results suggest that warming affects various aspects of overwintering physiology in P. rapae and may be detrimental depending on the frequency and variation of winter warming events. Further research is needed to ascertain the extent to which the effects of warming are felt among a broader set of populations of P. rapae, and among other species, in order to better predict how insects may respond to changes in winter thermal environments.

Cold tolerance, water balance, energetics, gas exchange, and diapause in overwintering brown marmorated stink bugs

Halyomorpha halys (Hemiptera: Pentatomidae) is an emerging pest which established in Ontario, Canada, in 2012. Halyomporpha halys overwinters in anthropogenic structures as an adult. We investigated seasonal variation in the cold tolerance, water balance, and energetics of H. halys in southwestern Ontario. We also induced diapause in laboratory-reared animals with short daylength at permissive temperatures and compared cold tolerance, water balance, energetics, and metabolism and gas exchange between diapausing and non-diapausing individuals. Halyomorpha halys that overwintered outside in Ontario all died, but most of those that overwintered in sheltered habitats survived. We confirm that overwintering H. halys are chill-susceptible. Over winter, Ontario H. halys depressed their supercooling point to c. -15.4 °C, and 50% survived a 1 h exposure to -17.5 °C. They reduce water loss rates over winter, and do not appear to significantly consume lipid or carbohydrate reserves to a level that might cause starvation. Overall, it appears that H. halys is dependent on built structures and other buffered microhabitats to successfully overwinter in Ontario. Laboratory-reared diapausing H. halys have lower supercooling points than their non-diapausing counterparts, but LT₅₀ is not enhanced by diapause induction. Diapausing H. halys survive desiccating conditions for 3-4 times longer than those not in diapause, through decreases in both respiratory and cuticular water loss. Diapausing H. halys do not appear to accumulate any more lipid or carbohydrate than those not in diapause, but do have lower metabolic rates, and are slightly more likely to exhibit discontinuous gas exchange.

Trans-generational effects on diapause and life-history-traits of an aphid parasitoid

Transgenerational effects act on a wide range of insects' life-history traits and can be involved in the control of developmental plasticity, such as diapause expression. Decrease in or total loss of winter diapause expression recently observed in some species could arise from inhibiting maternal effects. In this study, we explored transgenerational effects on diapause expression and traits in one commercial and one Canadian field strain of the aphid parasitoid Aphidius ervi. These strains were reared under short photoperiod (8:16 h LD) and low temperature (14 °C) conditions over two generations. Diapause levels, developmental times, physiological and morphological traits were measured. Diapause levels increased after one generation in the Canadian field but not in the commercial strain. For both strains, the second generation took longer to develop than the first one. Tibia length and wing surface decreased over generations while fat content increased. A crossed-generations experiment focusing on the industrial parasitoid strain showed that offspring from mothers reared at 14 °C took longer to develop, were heavier, taller with wider wings and with more fat reserves than those from mothers reared at 20 °C (8:16 h LD). No effect of the mother rearing conditions was shown on diapause expression. Additionally to direct plasticity of the offspring, results suggest transgenerational plasticity effects on diapause expression, development time, and on the values of life-history traits. We demonstrated that populations showing low diapause levels may recover higher levels through transgenerational plasticity in response to diapause-induction cues, provided that environmental conditions are reaching the induction-thresholds specific to each population. Transgenerational plasticity is thus important to consider when evaluating how insects adapt to changing environments.

Phenotypic plasticity, global change, and the speed of adaptive evolution

The role phenotypic plasticity might play in adaptation to the ongoing climate changes is unclear. Plasticity allows for the production of a diversity of intra-generational responses, whose inter-generational evolutionary consequences are difficult to predict. In this article, we review theory and empirical studies addressing this question in insects by considering three scenarios. The first scenario corresponds to adaptive plasticity that should lead to slow or no evolution. The second scenario is the case of non-adaptive phenotypic plasticity to new environmental conditions that should lead either to extinction or, on the contrary, to rapid evolutionary change. The third scenario deals with how plasticity alters the variance selection acts upon. These scenarios are then discussed by highlighting examples of empirical studies on insects. We conclude that more studies are needed to better understand the relationship between phenotypic plasticity and evolutionary processes in insects.

Life-history changes in the cold tolerance of the two-spot spider mite Tetranychus urticae: applications in pest control and establishment risk assessment

Lethal time50 (LTime50) and lethal temp (LTemp50) are commonly used laboratory indices of arthropod cold tolerance, with the former often being employed to predict winter survival in the field. In the present study, we compare the cold tolerance of different life-history stages (nondiapausing and diapausing females, as well as males and juveniles) of a major agricultural pest: the two-spot spider mite Tetranychus urticae Koch (Acarina: Tetranychidae). Diapausing females from European populations of this species are shown to be freeze avoiding, supercooling to -23.6 ± 0.37  °C and with an LTemp50 of -23.2 °C. However, nondiapausing females [supercooling point (SCP) -19.1 ± 0.49 °C, LTemp50 -14.32 °C], males (SCP -21.27 ± 0.52  °C, LTemp50 -16 °C) and juveniles (SCP -25.34 ± 0.29 °C, LTemp50 -18.3 °C) are subclassified as strongly chill tolerant juveniles. LTime50 is 148.3 days for non-acclimated diapausing females, whereas nondiapausing females, males and juveniles reach 50% mortality by 21.7 days. When individuals are acclimated at 10 °C for a period of 7 days, no effect is found. Cold tolerance is suggested to be a major contributor to the successful spread of T. urticae across temperate countries, although it is dependent on a diapause trait, suggesting a potential target for control. Winter field trial data from diapausing females indicate that LTime50 is a reliable indicator of winter survival even within diapause, supporting the use of these indices as a valuable component within environmental niche models for the prediction of future pest invasions.

Dynamics of Supercooling Ability and Cold Tolerance of the Alder Beetle (Coleoptera: Chrysomelidae)

Agelastica alni L. (Coleoptera: Chrysomelidae) is a common beetle pest of alder trees (Alnus incana L.) in forests and parks across Estonia. The supercooling ability and capacity to survive low temperature exposure changes temporally. Relatively high unimodal supercooling point (SCP) levels (with a mean value of -6 to -8°C) were characteristic of the beetles in September during their diapause induction period, in April when the beetles had terminated their diapause development and in May when they started to reproduce. During their deep diapause period the SCPs of beetles had a bimodal distribution. Some beetles decreased their SCPs to -14 to -19°C while others retained a high SCP value of -6 to -8°C. Most vulnerable to low temperature were overwintered active beetles in May; after 1 h exposure their LTemp50 (median lethal temperature) was -6.3°C. In September with the onset of diapause tolerance of beetles started to increase, LTemp50 = -7.7°C. Beetles were most cold tolerant during their deep diapause period with LTemp50 < -12.0°C. A. alni beetles use one of two different strategies for overwintering, some are freeze-tolerant while others are freeze-avoidant. The freeze-avoidant beetles with low SCP (-12 to -15°C) acquired greater cold tolerance than those with higher SCP (-6 to -8°C), with LTemp50 = -13.7°C and LTemp50 = -11°C, respectively.

Cold tolerance of third-instar Drosophila suzukii larvae

Drosophila suzukii is an emerging global pest of soft fruit; although it likely overwinters as an adult, larval cold tolerance is important both for determining performance during spring and autumn, and for the development of temperature-based control methods aimed at larvae. We examined the low temperature biology of third instar feeding and wandering larvae in and out of food. We induced phenotypic plasticity of thermal biology by rearing under short days and fluctuating temperatures (5.5-19°C). Rearing under fluctuating temperatures led to much slower development (42.1days egg-adult) compared to control conditions (constant 21.5°C; 15.7days), and yielded larger adults of both sexes. D. suzukii larvae were chill-susceptible, being killed by low temperatures not associated with freezing, and freezing survival was not improved when ice formation was inoculated externally via food or silver iodide. Feeding larvae were more cold tolerant than wandering larvae, especially after rearing under fluctuating temperatures, and rearing under fluctuating temperatures improved survival of prolonged cold (0°C) to beyond 72h in both larval stages. There was no evidence that acute cold tolerance could be improved by rapid cold-hardening. We conclude that D. suzukii has the capacity to develop at low temperatures under fluctuating temperatures, but that they have limited cold tolerance. However, phenotypic plasticity of prolonged cold tolerance must be taken into account when developing low temperature treatments for sanitation of this species.

Macro- and microclimatic interactions can drive variation in species' habitat associations

Many species are more restricted in their habitat associations at the leading edges of their range margins, but some species have broadened their habitat associations in these regions during recent climate change. We examine the effects of multiple, interacting climatic variables on spatial and temporal patterns of species' habitat associations, using the speckled wood butterfly, Pararge aegeria, in Britain, as our model taxon. Our analyses reveal that this species, traditionally regarded as a woodland-dependent insect, is less restricted to woodland in regions with warmer winters and warmer and wetter summers. In addition, over the past 40 years of climate change, the species has become less restricted to woodland in locations where temperature and summer rainfall have increased most. We show that these patterns arise mechanistically because larval growth rates are slower in open (i.e. nonwoodland) habitats associated with colder microclimates in winter and greater host plant desiccation in summer. We conclude that macro- and microclimatic interactions drive variation in species' habitat associations, which for our study species resulted predominantly in a widening of habitat associations under climate change. However, species vary in their climatic and nonclimatic requirements, and so complex spatial and temporal patterns of changes in habitat associations are likely to be observed in future as the climate changes.

What Can Plasticity Contribute to Insect Responses to Climate Change?

Plastic responses figure prominently in discussions on insect adaptation to climate change. Here we review the different types of plastic responses and whether they contribute much to adaptation. Under climate change, plastic responses involving diapause are often critical for population persistence, but key diapause responses under dry and hot conditions remain poorly understood. Climate variability can impose large fitness costs on insects showing diapause and other life cycle responses, threatening population persistence. In response to stressful climatic conditions, insects also undergo ontogenetic changes including hardening and acclimation. Environmental conditions experienced across developmental stages or by prior generations can influence hardening and acclimation, although evidence for the latter remains weak. Costs and constraints influence patterns of plasticity across insect clades, but they are poorly understood within field contexts. Plastic responses and their evolution should be considered when predicting vulnerability to climate change-but meaningful empirical data lag behind theory.

Maternal response to environmental unpredictability

Mothers are expected to use environmental cues to modify maternal investment to optimize their fitness. However, when the environment varies unpredictably, cues may not be an accurate proxy of future conditions. Under such circumstances, selection favors a diversifying maternal investment strategy. While there is evidence that the environment is becoming more uncertain, the extent to which mothers are able to respond to this unpredictability is generally unknown. In this study, we test the hypothesis that Daphnia magna increase the variance in maternal investment in response to unpredictable variation in temperature consistent with global change predictions. We detected significant variability across temperature treatments in brood size, neonate size at birth, and time between broods. The estimated variability within-brood size was higher (albeit not statistically significant) in mothers reared in unpredictable temperature conditions. We also detected a cross-generational effect with the temperature history of mothers modulating the phenotypic response of F1's. Notably, our results diverged from the prediction that increased variability poses a greater risk to organisms than changes in mean temperature. Increased unpredictability in temperature had negligible effects on fitness-correlated traits. Mothers in the unpredictable treatment, survived as long, and produced as many F1's during lifetime as those produced in the most fecund treatment. Further, increased unpredictability in temperature did not affect the probability of survival of F1's. Collectively, we provide evidence that daphnia respond effectively to thermal unpredictability. But rather than increasing the variance in maternal investment, daphnia respond to uncertainty by being a jack of all temperatures, master of none. Importantly, our study highlights the essential need to examine changes in variances rather than merely on means, when investigating maternal responses.

Meat Feeding Restricts Rapid Cold Hardening Response and Increases Thermal Activity Thresholds of Adult Blow Flies, Calliphora vicina (Diptera: Calliphoridae)

Virtually all temperate insects survive the winter by entering a physiological state of reduced metabolic activity termed diapause. However, there is increasing evidence that climate change is disrupting the diapause response resulting in non-diapause life stages encountering periods of winter cold. This is a significant problem for adult life stages in particular, as they must remain mobile, periodically feed, and potentially initiate reproductive development at a time when resources should be diverted to enhance stress tolerance. Here we present the first evidence of protein/meat feeding restricting rapid cold hardening (RCH) ability and increasing low temperature activity thresholds. No RCH response was noted in adult female blow flies (Calliphora vicina Robineau-Desvoidy) fed a sugar, water and liver (SWL) diet, while a strong RCH response was seen in females fed a diet of sugar and water (SW) only. The RCH response in SW flies was induced at temperatures as high as 10°C, but was strongest following 3h at 0°C. The CTmin (loss of coordinated movement) and chill coma (final appendage twitch) temperature of SWL females (-0.3 ± 0.5°C and -4.9 ± 0.5°C, respectively) was significantly higher than for SW females (-3.2 ± 0.8°C and -8.5 ± 0.6°C). We confirmed this was not directly the result of altered extracellular K+, as activity thresholds of alanine-fed adults were not significantly different from SW flies. Instead we suggest the loss of cold tolerance is more likely the result of diverting resource allocation to egg development. Between 2009 and 2013 winter air temperatures in Birmingham, UK, fell below the CTmin of SW and SWL flies on 63 and 195 days, respectively, suggesting differential exposure to chill injury depending on whether adults had access to meat or not. We conclude that disruption of diapause could significantly impact on winter survival through loss of synchrony in the timing of active feeding and reproductive development with favourable temperature conditions.

Phenotypic plasticity of HSP70s gene expression during diapause: signs of evolutionary responses to cold stress among Soybean Pod Borer populations (Leguminivora glycinivorella) in Northeast of China

The soybean pod borer (Leguminivora glycinivorella Matsumura) successfully survives the winter because of its high expression of 70-kDa heat shock proteins (HSP70s) during its overwintering diapause. The amount of HSP70s is different under different environmental stresses. In this study, inducible heat shock protein 70 and its constitutive heat shock cognate 70 were cloned by RT-PCR and RACE. These genes were named Lg-hsp70 and Lg-hsc70, respectively. Gene transcription and protein expression after cold stress treatment (5°C to −5°C) were analyzed by western blotting and by qRT-PCR for four populations that were sampled in the northeast region of China, including Shenyang, Gongzhuling, Harbin and Heihe, when the soybean pod borer was in diapause. As the cold shock temperature decreased, the levels of Lg-HSP70s were significantly up-regulated. The amount of cold-induced Lg-HSP70s was highest in the southernmost population (Shenyang, 41°50′N) and lowest in the northernmost population (Heihe, 50°22′N). These results support the hypothesis that the soybean pod borer in the northeast region of China displays phenotypic plasticity, and the accumulation of Lg-HSP70s is a strategy for overcoming environmental stress. These results also suggest that the induction of HSP70 synthesis, which is a complex physiological adaptation, can evolve quickly and inherit stability.

Application of functional 'Omics' in environmental stress physiology: insights, limitations, and future challenges

Omic technologies have revolutionised how environmental physiologists investigate stress response pathways. To date, however, omic screens typically constitute simple presence/absence correlations, and fall short of explaining mechanism. Disentangling function necessitates hypothesis-driven manipulation of selected molecular signals, and a systems level view will only come from more detailed tissue-specific and time series sampling. The increasing accessibility of omic applications means that species can be selected based on Krogh principles, but focus also needs to be given to core models where multi-platform approaches can be combined to provide a deeper understanding. This review highlights recent technological and intellectual advances in the application of omics to understanding insect stress adaptation, and sets out how to address remaining knowledge gaps.