It is widely accepted that the existence of giant insects during the late Paleozoic was driven by elevated atmospheric O2 levels, in light of the proposal that oxygen diffusion through the tracheal system constrains insect body size. However, a recent study demonstrates that this assumption is incorrect, highlighting the need to consider alternative or complementary explanations.

Environmental temperature strongly influences insect metabolic rate (MR), yet the thermal sensitivity of MR across developmental stages remains understudied in hemimetabolous species. Here we quantified resting metabolic rate (RMR) thermal sensitivity in Rhodnius prolixus, a hemimetabolous insect and an important Chagas disease vector. For that, we measured real-time CO2 production by open flow-respirometry as a proxy for MR at six temperatures (10, 15, 20, 25, 30, and 35 °C) across all life stages. We found a stage-specific thermal sensitivity of the RMR. Instantaneous Q10 estimates revealed ontogenetic variation: early nymphs exhibited higher thermal sensitivity at cooler temperatures and lower sensitivity at warmer temperatures, while adults maintained constant Q10 values across the thermal range. These findings provide novel insights into thermal biology of hemimetabolous insects and show that developmental stage influences metabolic responses to temperature. Understanding these patterns is crucial for predicting how climate warming may affect the physiology, population dynamics and disease transmission potential of this vector species.

IntroductionUrban landscapes are increasingly recognized as key arenas for biological invasions, yet the mechanisms enabling the local coexistence of multiple highly invasive species remain poorly understood. Urban habitat fragmentation generates mosaics of habitat patches that differ in size, isolation, and microhabitat complexity, shaping ant community structure and competitive interactions. MethodsHere, we investigated ant assemblages across a mosaic of urban habitat patches within a university campus in Buenos Aires, Argentina, focusing on four globally invasive ant species (Wasmannia auropunctata, Linepithema humile, Nylanderia fulva, and Solenopsis invicta) near the southern limit of their native ranges. We quantified species richness, abundance and composition using pitfall traps and evaluated species-specific indicators of food discovery, recruitment, and dominance using standardized bait experiments.ResultsAnt assemblages differed significantly among habitat patches, with marked spatial variation in richness, diversity, and species composition. Contrary to expectations of rigid dominance hierarchies, no single species consistently dominated across patches. Nylanderia fulva showed the highest numerical abundance and discovery efficiency, L. humile exhibited the strongest recruitment ability, and W. auropunctata displayed localized dominance near nesting areas, while S. invicta was rare and competitively subordinate. Ordination and multivariate analyses indicated strong spatial structuring of assemblages, consistent with the influence of urban fragmentation and patch-level heterogeneity.Discussion/ConclusionOverall, our results support a metacommunity perspective in which invasive ant coexistence in urban systems is mediated by context-dependent competitive interactions rather than fixed dominance hierarchies. By emphasizing the role of fine-scale spatial structure, this study provides a nuanced, system-specific contribution to understanding invasive ant dynamics in urban environments.

Biological invasions increasingly threaten ecosystems and agriculture. The spotted-wing drosophila, Drosophila suzukii, has been recognized as a highly polyphagous invasive pest. In South America, many of D. suzukii collecting sites overlap with native cactus species distribution and cacti are available resources throughout the year, including times when the crops are absent. However, D. suzukii capacity to develop on cactus hosts has not been experimentally evaluated. Here we evaluate the prickly pear cactus, O. sulphurea, as a potential alternative host by conducting no-choice oviposition assays and rearing larvae on a semi-natural cactus diet. We compared the viability, developmental time, morphological and reproductive traits, and fatty acid profiles of flies reared on cactus against two laboratory diets. Females laid eggs on cactus tissue, and larvae successfully completed development with fitness parameters and fatty acid profiles of adults comparable to the standard diets. These findings indicate that O. sulphurea could be a suitable breeding resource for D. suzukii, suggesting that it may serve as an alternative host during periods in which cultivated fruits become unavailable. These results may have implications for pest management programs and ecological dynamics.

Abstract Feeding behavior in blood-sucking insects relies on gustatory evaluation to decide on sustained ingestion, yet quantifying this process from electromyogram (EMG) recordings is labor-intensive. Here we developed MyoRec, an automated computational framework employing machine learning to analyse EMG signals from the triatomine bug Rhodnius prolixus . Using recordings under appetitive and aversive conditions, a convolutional neural network detected ingestion events with 97.7% accuracy. Automated analysis revealed distinct feeding dynamics, with prolonged ingestion and higher pumping frequency under appetitive stimuli, compared to rapid feeding cessation under aversive stimuli. MyoRec substantially reduces analysis time while maintaining accuracy, providing a scalable tool to investigate how gustatory cues modulate feeding decisions in hematophagous insects.

We investigated the correlated evolution of fitness‐related traits in cactophilic species Drosophila buzzatii Patterson & Wheeler and D. koepferae Fontdevila & Wasserman (Drosophilidae, Drosophilini) as an indirect response to adaptation to high concentrations of phytochemicals in their host plant ( Trichocereus terscheckii Briton & Rose). Specifically, we examined whether the experimental evolution of phytochemical tolerance influenced metabolic rate, fecundity, longevity, and starvation resistance. Our findings reveal that adaptation to phytochemical defenses led to correlated responses in both species, likely driven by genetic correlations and energy allocation strategies. Notably, sexual dimorphism was evident, underscoring the significance of sex‐specific effects in the adaptive process. The tolerant phenotypes of each species emerged from distinct pleiotropic backgrounds, with D. buzzatii exhibiting more correlated responses than D. koepferae , suggesting a deeper genetic perturbation or response during the experimental evolution. This study demonstrates how exploiting a marginally used host can impose costs on crucial fitness‐related traits, such as adult lifespan and reproductive output. Moreover, ignoring variation in tolerance to phytotoxins would overlook the diversity of responses across species. This variation is essential for understanding how different species manage to exploit toxic plants. Neglecting this aspect would result in a simplified view of insect–plant interactions, failing to account for the nuanced ways in which insects evolve strategies to detoxify or avoid harmful substances.

Global warming influences organisms through direct and indirect effects on abiotic and biotic factors, such as temperature and food availability. This study examines how developmental diet and thermal regime influence fitness and thermal tolerance in Drosophila buzzatii, a cactophilic fly with a broad thermal tolerance, and a model organism in evolutionary ecology. Using a factorial design, we reared flies at 10 °C and 25 °C, with and without daily thermal fluctuations, on two natural cactus-based diets and a standard lab diet. We measured viability, development time, wing length, ovariole number, chill coma recovery time and fatty acid composition. We found synergistic effects between cactus diet and thermal daily fluctuations, overcoming the complete loss of viability observed at 10 °C and mitigating the negative effects shown at 25 °C. In addition, flies reared at a low fluctuating temperature had greater cold tolerance and a higher unsaturated-to-saturated fatty acid ratio, supporting the homeoviscous adaptation hypothesis. These findings suggest D. buzzatii may overwinter as larvae and pupae in temperate areas and highlight the importance of diet-thermal interactions in shaping insect responses to climate change.

Worldwide, with the decline of natural habitats, species with reduced niche breadth (specialists) are at greater risk of extinction as they cannot colonise or persist in disturbed habitat types. However, the role of thermal tolerance as a critical trait in understanding changes in species diversity in disturbed habitats, e.g., due to forest replacement by tree plantations, is still understudied. To examine the role of thermal tolerance on the responses of specialist and generalist species to habitat disturbances, we measured and compared local temperature throughout the year and thermotolerance traits [upper (CTmax) and lower (CTmin) thermal limits] of the most abundant species of spiders from different guilds inhabiting pine tree plantations and native Atlantic Forests in South America. Following the thermal adaptation hypothesis, we predicted that generalist species would show a wider thermal tolerance range (i.e., lower CTmin and higher CTmax) than forest specialist species. As expected, generalist species showed significantly higher CTmax and lower CTmin values than specialist species with wider thermal tolerance ranges than forest specialist species. These differences are more marked in orb weavers than in aerial hunter spiders. Our study supports the specialisation disturbance and thermal hypotheses. It highlights that habitat-specialist species are more vulnerable to environmental changes associated with vegetation structure and microclimatic conditions. Moreover, thermal tolerance is a key response trait to explain the Atlantic Forest spider's ability (or inability) to colonise and persist in human-productive land uses.

BACKGROUND: Wheat grain containers or silos can be perfect habitats for insects, which generate large economic losses to grain production. Natural alternatives to synthetic insecticides have grown in popularity because of health, economic and ecological issues. Diatomaceous earth is a natural compound that has an insecticide effect by enhancing an insect's dehydration with no toxicity on mammals including humans. The aim of this study is to confirm the effect of diatomaceous earth as an insecticide for the wheat grain pest, the red flour beetle Tribolium castaneum (Coleoptera: Tenebrionidae) and demonstrate its underlying mechanisms as an insecticide by open-flow respirometry and scanning electron microscopy. RESULTS: Survival bioassays of T. castaneum revealed a dose-dependent insecticide effect of diatomaceous earth. Gravimetric measurements showed that 2 days exposure to diatomaceous earth produces a significant increase of mass loss. Open-flow respirometry measurements showed an increase of total water emission rate on insects due to an increase of both, respiratory and cuticular water loss. Our study revealed that diatomaceous earth produces an increase of insect's cuticle permeability, which is responsible for elevated cuticular water loss. Scanning electron microscopy images provided visual evidence of the lipid absorbent properties of diatomaceous earth particles, and showed a tendency for higher, although not significant, damaged area of the cuticle's surface from diatomaceous earth treated insects compared to control ones. CONCLUSION: With state-of-the art techniques like open-flow respirometry and scanning electron microscopy, we demonstrated the underlying mechanism of diatomaceous earth as an insecticide and provided new cues for understanding the properties of the cuticle and its ecological importance. (c) 2024 Society of Chemical Industry.

Immature mosquitoes are thought to breathe only atmospheric air through their siphons despite reports of prolonged submerged survival. We studied the survival of last-instar larvae of Aedes aegypti fully submerged at different temperatures and measured the oxygen consumption from air and water-dissolved larvae and pupae of this species under different conditions. Larvae survived much longer than expected, reaching 50% mortality only after 58, 10, and 5 days at 15°, 25°, and 35 °C, respectively. Larval to pupa molt was only observed in larvae with access to air, whereas individuals kept submerged never molted. Although most of the oxygen was obtained from the air, larvae obtained 12.72% of their oxygen from the water, while pupae took only 5.32%. In both media, temperature affected the respiration rate of the larvae, with relatively close Q10 values (1.56 and 1.83 for water and air, respectively). A similar pattern of O2 consumption was observed in Ae. albopictus, whose larvae obtained 12.14% of their oxygen from the water. The detailed quantification of oxygen consumption by mosquito larvae showed that water-dissolved oxygen is not negligible and physiologically relevant, challenging the idea that mosquito larvae only breathe atmospheric oxygen.

•D. suzukii females have broader thermotolerance range and lower Q10 than males.•Cold anesthesia detrimentally affects heat tolerance.•No effect of brief exposure to anesthesia on MR or cold tolerance.•Sex differences in MR is due to mass.

Temperate species, contrary to their tropical counterparts, are exposed not only to thermally variable environments with low temperatures but also to long winters. Different selective pressures may have driven divergent physiological adaptations in closely related species with different biogeographic origins. To survive unfavourable winter conditions, Drosophila species in temperate areas generally undergo a period of reproductive dormancy, associated with a cold-induced cessation of oogenesis and metabolic reorganization. This work aims to compare cold tolerance and metabolic signatures of cold-exposed females exhibiting different reproductive maturity status (mature and immature females) of four Drosophila species from tropical vs. temperate origins. We expected that the capacity for delayed reproduction of immature females could result in the redirection of the energy-related metabolites to be utilized for surviving the cold season. To do so, we studied an array of 45 metabolites using quantitative target GC-MS profiling. Reproductively immature females of temperate species showed the lower CTmin and the faster chill coma recovery time (i.e. the most cold-tolerant group). Principal component analysis captured differences across species, but also between reproductive maturity states. Notably, temperate species exhibited significantly higher levels of glucose, alanine, and gluconolactone than tropical ones. As proline and glycerol showed higher abundances in immature females of temperate species compared to the levels exhibited by the rest of the groups, we reasoned that glucose and alanine could serve as intermediates in the synthesis of these compatible solutes. All in all, our findings suggest that cold-exposed females of temperate species accumulate energy-related and protective metabolites (e.g. glycerol and proline) while delaying reproduction, and that these metabolites are relevant to cold tolerance even at modest concentrations.

It is well known that viscosity reduces the intake rates in nectar-feeding insects, such as nectivorous ants, though it remains unclear whether viscosity imposes a higher energy investment in these insects, and how this affects their feeding motivation. To address this issue, we studied feeding behavior, metabolism, and pharyngeal pump activity in the carpenter ant Camponotus mus during ingestion of ad libitum sucrose solutions. In some solutions tylose was added to modify viscosity without changing its sucrose concentration, in a way that allowed comparing: (1) two solutions with the same viscosity and different sucrose concentration (10 T and 50), and (2) two solutions with different viscosity and the same sucrose concentration (50 and 50 T). The viscosity increase was detrimental to the metabolic rate and energy balance. Ants feeding on a solution with high sucrose concentration and increased viscosity (50 T) spent extra-time until reaching a crop load similar to that reached by ingesting the solution without tylose (50). For all solutions offered, ants started feeding with the same pharyngeal pump frequencies, reflecting a similar motivation. Interesting, when ants fed on a low sucrose concentration and increased viscosity solution (10 T), their pump frequencies dropped rapidly respect to the pure-sucrose solution (50). On the contrary, pump frequencies for 50 and 50 T remained similar until the end of the intake. Since the pump frequency is strongly modulated by the ant motivation, an increase in viscosity with low sucrose content, demotivates the ants rapidly, suggesting a rapid integration of different kinds of information about the food value. Our results helped to understand how nectivorous ants could modulate their foraging decision-making.

Triatoma infestans (Klug, 1834), the main vector of Chagas disease in Latin America, is regularly controlled by spraying the pyrethroid deltamethrin, to which some populations have developed resistance. The three main mechanisms of resistance are 1) metabolic resistance by overexpression or increased activity of detoxifying enzymes, 2) target site mutations, and 3) cuticle thickening/modification. We use open-flow respirometry to measure real-time H2O loss rate (V˙H2O) and CO2 production rate (V˙CO2), on nymphs from susceptible and resistant populations before and after exposure to the insecticide to understand the underlying mechanisms of resistance in live insects. Lack of differences in V˙H2O between populations suggested that cuticular thickness/composition is not acting as a relevant resistance mechanism. Similarly, there was no difference in resting V˙CO2, suggesting a trade-off between resistance mechanisms and other physiological processes. The increment in V˙CO2 after application of deltamethrin was similar in both populations, which suggested that while enhanced enzymatic detoxification may play a role in resistance expression in this population, the main mechanism involved should be a passive one such as target site mutations. Open-flow respirometry provided useful evidence for evaluating the mechanisms involved in deltamethrin resistance. Using this technique could improve efficiency of scientific research in the area of insecticide resistance management, leading to a faster decision making and hence improved control results.

BACKGROUND:Leaf-cutting ants (LCAs) are amongst the most important forestry pests in South America. Currently, their control is carried out almost exclusively through the application of toxic baits of restricted use. Here we evaluate a push-pull strategy (i.e., the simultaneous use of attractant and repellent stimuli in order to divert pests) to manage LCAs Acromyrmex spp. in young willow plantations in the area of Delta of the Parana River, Argentina, a wetland ecosystem. First, we surveyed ants' selection of farmland vegetation during one year. Then, we estimated ants' preferences between the willow Salix babylonica and a subsample of plant species from farmland vegetation under laboratory conditions. Finally, we designed and performed a fully crossed experimental field assay to evaluate a push-pull strategy by using farmland vegetation as pull stimulus.RESULTS:We surveyed 39 plant species in the area, 19 of which had been foraged by LCAs along the year. Plants were selected by species, not by abundance. In the lab, ants showed similar preference for the cultivated willow and the subsample of plant species. Push-pull was the only treatment that maintained willow remaining vegetation above 60-80% at the end of the growing season.CONCLUSIONS:For the first time the push-pull strategy was evaluated in social insects. We demonstrated that it can be successfully used to manage LCAs in young willow plantations. Our strategy generates biodiversity, which can improve the ecosystem functioning, and it can be easily implemented by producers since its design is based on regular willow plantations.

The sense of taste provides information about the "good" or "bad" quality of a food source, which may be potentially nutritious or toxic. Most alkaloids taste bitter to humans, and because bitter taste is synonymous of noxious food, they are generally rejected. This response may be due to an innate low palatability or due to a malaise that occurs after food ingestion, which could even lead to death. We investigated in the kissing bug Rhodnius prolixus, whether alkaloids such as quinine, caffeine and theophylline, are merely distasteful, or if anti-appetitive responses are caused by a post-ingestion physiological effect, or both of these options. Although anti-appetitive responses were observed for the three alkaloids, only caffeine and theophylline affect metabolic and respiratory parameters that reflected an underlying physiological stress following their ingestion. Furthermore, caffeine caused the highest mortality. In contrast, quinine appears to be a merely unpalatable compound. The sense of taste helps insects to avoid making wrong feeding decisions, such as the intake of bitter/toxic foods, and thus avoid potentially harmful effects on health, a mechanism preserved in obligate hematophagous insects.

Noonan syndrome and related disorders are caused by mutations in genes encoding for proteins of the RAS-ERK1/2 signaling pathway, which affect development by enhanced ERK1/2 activity. However, the mutations’ effects throughout adult life are unclear. In this study, we identify that the protein most commonly affected in Noonan syndrome, the phosphatase SHP2, known in Drosophila as corkscrew (CSW), controls life span, triglyceride levels, and metabolism without affecting ERK signaling pathway. We found that CSW loss-of-function mutations extended life span by interacting with components of the insulin signaling pathway and impairing AKT activity in adult flies. By expressing csw-RNAi in different organs, we determined that CSW extended life span by acting in organs that regulate energy availability, including gut, fat body and neurons. In contrast to that in control animals, loss of CSW leads to reduced homeostasis in metabolic rate during activity. Clinically relevant gain-of-function csw allele reduced life span, when expressed in fat body, but not in other tissues. However, overexpression of a wild-type allele did not affect life span, showing a specific effect of the gain-of-function allele independently of a gene dosage effect. We concluded that CSW normally regulates life span and that mutations in SHP2 are expected to have critical effects throughout life by insulin-dependent mechanisms in addition to the well-known RAS-ERK1/2-dependent developmental alterations.

Temperature is recognized as the most influential abiotic factor on the distribution and dispersion of most insect species including Rhodnius prolixus (Stål, 1859) and Triatoma infestans (Klug, 1834), the two most important Chagas disease vectors. Although, these species thermotolerance range is well known their plasticity has never been addressed in these or any other triatomines. Herein, we investigate the effects of acclimation on thermotolerance range and resistance to stressful low temperatures by assessing thermal critical limits and 'chill-coma recovery time' (CCRT), respectively. We found positive effects of acclimation on thermotolerance range, especially on the thermal critical minimum of both species. In contrast, CCRT did not respond to acclimation in either. Our results reveal the plasticity of these Triatomines thermal tolerance in response to a wide range of acclimation temperatures. This presumably represents a physiological adaptation to daily or seasonal temperature variation with concomitant improvement in dispersion potential.

Species distribution models based on the correlation of bioclimatic variables and presence spatial data-points are useful for recognizing species habitat suitability. However, they have limitations in predicting the introduced ranges of invasive species that could be overcome by using species eco-physiological traits. By combining bioclimatic variables with thermal tolerance plasticity of the highly invasive little fire ant, Wasmannia auropunctata, we intend to better understand the mechanism underlying its current and future distributions. To this end, we performed: (1) laboratory physiological experiments to assess thermal tolerances (CTmin and CTmax) and evaluate the effect of acclimation (laboratory) and acclimatization (nature) on these variables, (2) behavioral foraging observations in the field, (3) a correlative and a simple mechanistic SDM. Briefly, physiological results showed a modulation of the CTmax and CTmin by different acclimation temperatures and by seasonal thermal acclimatization. In the field, worker foraging activity begins at environmental temperatures just above (less than 1 °C) the lowest CTmin recorded in the laboratory. At the global scale, CTmin constitutes a key physiological trait that, when linked with the minimum temperature of the coldest month, could explain the southernmost limit of W. auropunctata native distribution and its physiological capacity to expand in the Mediterranean region. The eco-physiological approach carried out here may help explain the current distribution and predict potential spread of populations when there is no certain information about the whole distribution of the species or under a changing environment. The latter is of great importance especially when analyzing invasive insects, pests or disease vectors.