Ecological Entomology

Morphological variation in insects can indicate responses to habitat change and land use intensification, with potential consequences for trophic interactions. In insect host-parasitoid systems, host body is often a key determinant of offspring development and emergence success, as well as parasitoid host-selection behavior. Yet, most studies in agricultural landscapes have focused on size variation in crop-associated insects (i.e.: pests, pollinators and enemies), leaving those relying on non-crop resources largely unexplored. Here, we investigated how agroenvironmental contexts and trophic resource availability influence puparial size in Protocalliphora sialia (Diptera: Calliphoridae), an obligate hematophagous ectoparasite of Tree Swallow (Tachycineta bicolor) nestlings. We further tested whether puparial size affects emergence probability and risk of parasitoidism by Nasonia spp. (Hymenoptera: Pteromalidae) jewel wasps. Using 1,513 P. sialia puparia from 88 nests within a nest-box monitoring system spanning a 10,200-km^2 east-west intensification gradient in southern Quebec, Canada, we evaluated how agrointensive contexts, avian host availability, and ectoparasite densities influence puparial size, parasitoidism risk, and emergence success. The agricultural context appears to shape puparial size through survival biases and/or altered growth rates. In agroextensive contexts (i.e.: pastures, forages with high tree cover), where Protocalliphora are more numerous, P. sialia puparia were smaller and exhibited greater size variation. Conversely, in agrointensive environments (maize and soybeans monocultures with higher doses of pesticides), where Protocalliphora are fewer, small individuals were underrepresented, suggesting a selective mortality in P. sialia population. However, puparial size explained less than 10% of the variation in emergence or parasitism, likely reflecting consistently high parasitic pressure from Nasonia wasps, which infested 50-90% of puparia, depending on site and year. Our findings highlight the importance of selective mortality in structuring trait distributions and modulating multi-trophic interactions in human-modified landscapes.

Colony defence is critical for the survival of wild honeybees but presents a challenge for local populations and beekeepers. Apis mellifera scutellata is an important pollinator in its native range, a large area of Southern and Eastern Africa 1, but is reputed for its explosive temperament. Here, we present data demonstrating that this behaviour is only exhibited by a small fraction of colonies, while others are relatively docile. This sheds new light on this subspecies and on its likely evolutionary trajectory. We further characterize the different elements of this defensive response and compare them to that of A. m. carnica and A. m. mellifera. We show that each subspecies invests differently in the two steps of the behavioural sequence (alert and attack). Furthermore, our results suggest that the task of attacking is carried out by specialized workers in carnica, but not in the other subspecies tested, highlighting subtle differences in colony organization across subspecies. Finally, we discovered that defenders from A. m. scutellata and scutellata-hybrid colonies can locate a target that was stung up to 2 h and 3 h earlier, respectively, whereas European bees could only do so for 30 min. This long-term marking could confer an advantage against returning predators with few weak points, such as honey badgers and humans wearing protective clothing. Overall, we offer a fresh perspective on this controversial but important subspecies of honeybees, with implications for both future studies and daily management.

Fallen fleshy fruits are temporary resource patches that can support diverse but transient invertebrate assemblages, yet their successional dynamics remain poorly documented in tropical landscapes modified by human activity. We examined heterotrophic succession on fallen ripe guava fruits, Psidium guajava, in a tropical grove in Barasat, West Bengal, India. Eight fruits were placed in exposed and shaded microhabitats and followed from fresh to degraded stages over 22 days. Invertebrates were recorded using repeated scan sampling, and daily observations for each fruit were analysed for taxon richness, Shannon diversity, total peak relative abundance, community composition and indicator taxa associated with decomposition stages. Across 141 daily fruit observations, we recorded 44 invertebrate taxa. Taxon richness, Shannon diversity and total peak relative abundance were highest during fresh and pre rotten stages and declined sharply during post rotten and degraded stages. Decomposition stage was the strongest predictor of alpha diversity, resource use intensity and community composition, whereas differences between exposed and shaded microhabitats were weaker. Indicator taxa showed clear successional replacement: fresh fruits were associated with drosophilid and tephritid flies; fresh and pre rotten fruits with nitidulid beetles and ants; and later stages with collembolans, staphylinids, blattodeans and other taxa associated with detrital stages. Ants, especially Pheidole sp., were conspicuous resource users and showed guarding, hoarding, predation and pulp or seed removal behaviour, although their effects on other taxa remain observational. These results show that fallen guava fruits function as ephemeral heterotrophic resource patches, supporting rapid invertebrate turnover at fine temporal scales in a tropical grove.

Feathers incorporated into bird nests are thought to provide multiple benefits, including thermal insulation and protection against nest-dwelling ectoparasites. For instance, in Swallows, it has been suggested that feathers influence infestations by Protocalliphora blow flies either by acting as a physical barrier between larvae and nestlings or through chemical compounds associated with preen oil. However, empirical evidence for an antiparasitic effect of feathers remains equivocal. Using 1,100 naturally infested Tree Swallow (Tachycineta bicolor) nests collected from a nest-box study system monitored in southern Quebec, Canada, between 2004 and 2018, we tested whether nest mass and feather abundance influenced hematophagous ectoparasites (Protocalliphora spp.) loads. We further assessed whether feather abundance directly affected body size using measurements of 1,513 P. sialia puparia, and emergence success using data from 961 Protocalliphora spp. puparia. Nest mass was positively associated with feather abundance, and both variables showed very weak positive relationships with parasite abundance. Feather abundance was unrelated to puparium size nor parasite emergence success. Our results provide no support for an anti-parasitic effect of feather lining within Tree Swallow nests. Using one of the largest datasets assembled to date on feather-lined nests and avian blow flies, we found no evidence that feather abundance impairs Protocalliphora density, development or emergence success. However, our findings do not preclude potential effects of feathers on other ectoparasites or microorganisms with different life histories. Future studies simultaneously monitoring multiple parasite taxa (such as fleas, mites, or bacteria) may therefore be needed to fully evaluate the ecological consequences of feather lining within avian nests.

When mating among genetically related individuals results in inbreeding depression, various behaviors and life-history traits evolve to favor outbreeding. Long-range sexual communication following natal dispersal is one such adaptation. In parasitoid wasps with single-locus complementary sex determination (sl-CSD), inbreeding increases the production of unviable or sterile diploid males. Mastrus ridens is such a species, with a genetic load underpinned by sl-CSD, combined with a high potential for sibmating because siblings emerge in close proximity from the same host and become sexually active shortly after emergence. With this context in mind, we investigated the mate-finding strategy of M. ridens using complementary behavioral, chemical, and electrophysiological approaches. Wind-tunnel bioassays and field experiments showed that males orient toward virgin females and, to a lesser extent, mated females. This attraction from a distance appeared to be the sole form of conspecific attraction. Chemical analyses using static and dynamic headspace sampling and solvent extracts, followed by GC-MS, revealed several potential pheromonal candidates, including methyl 6-methylsalicylate. This compound elicited reproducible antennal responses in males in GC-EAD recordings. Altogether, our results suggest that mate finding in M. ridens is guided by a volatile sex pheromone emitted by females, with methyl 6-methylsalicylate as one putative component. Such mate-finding mechanisms promote outbreeding and may explain the low proportion of unfit diploid males observed in natural populations. Surprisingly, chemical analyses suggested that males also emit this compound, whereas neither males nor females showed behavioral responses to males. This apparent discrepancy suggests that attraction may depend on a more complex pheromonal signal and opens further avenues for investigation.

Diurnal ectotherms in hot and dry ecosystems face an acquisition trade-off between maximizing collective energy intake and minimizing individual exposure time. We employed optimal foraging and thermoregulation models to examine the surface foraging and thermoregulatory strategies of Pogonomyrmex barbatus foragers in response to habitat warming in a tropical deciduous forest. Foraging activity was evaluated using field-based thermal performance curves (fTPCs) for individual foraging speed and collective foraging success. Thermoregulation was assessed through indices of thermal unsuitability, as well as thermoregulatory effectiveness and exploitation. Our results show that afternoon conditions were significantly hotter and drier than those in the morning. Furthermore, the decoupling of fTPCs was dynamic; while the optimal temperature (Topt) for individual foraging speed remained stable at 44 degrees C, the Topt for collective foraging success shifted from 35 degrees C in the morning to 41 degrees C in the afternoon. This shift in foraging strategy, driven by stressful afternoon conditions, was reflected in a transition of the thermoregulatory strategy. Specifically, the probability of foraging activity decreased as thermal unsuitability increased, with a lower baseline in the afternoon. The thermoregulatory exploitation dropped from 94% in the morning to 63% in the afternoon. Based on thermoregulatory effectiveness, foragers transitioned from an active thermoregulatory strategy in the morning to a thermoconformist strategy in the afternoon while foraging on the surface. So, the observed colonies optimized the balance between individual foraging speed and collective foraging success through a thermoregulatory strategy that was primarily spatial in the morning and strictly temporal in the afternoon. A comparison with historical data from the same site reveals a 40% contraction in the total daily foraging window since 2013.

A longstanding question in evolution is if similar morphologies shared by distantly related organisms facing similar environmental pressures belie similar functions. The carnivorous pitcher form has evolved in three distinct plant lineages and encompasses a suite of convergent morphological traits, providing a natural experiment to test hypothesized links between morphology and function. Multiple pitcher plant species possess fenestrations (i.e., small windows) that let light pass through the pitcher leaf. While research on one species, Nepenthes aristolochioides, demonstrates that fenestrations manipulate light to create false exits and increase prey capture, whether this convergent morphology serves this convergent function in other pitcher species remains unresolved. We explored the function of fenestrations in two additional species of pitcher plants, Nepenthes klossii and Cephalotus follicularis, where the morphology and function of fenestration were previously unexplored. We inspected micromorphology of pitcher structure, conducted an insect bioassay with live plants to test for links between morphology and function, and quantified traits associated with light manipulation from herbarium specimens. Both species exhibited fenestration and related pitcher morphology similar to N. aristolochioides. Yet our experiments did not reveal a significant effect of light passing through fenestrations on fly capture for these two species. Key differences between these species and the previously investigated species may be the presence of wax crystals and the absence of viscoelastic fluid. While future studies may uncover weak to moderate light manipulation function not detected in our study, our data do not support convergent function in these distantly related, morphologically similar species.

Fluctuating asymmetry (FA) is widely used as a proxy for developmental instability, although reduced rather than increased FA, has occasionally been reported under particularly challenging conditions, possibly because environmental filtering removes less developmentally stable individuals. Here, we investigated temporal variation in wing shape asymmetry in males of Drosophila sturtevanti collected in 2022, 2024, and 2026 at the same sampling site, an urban Atlantic Forest fragment. Sampling in 2022 and 2026 were completed during single field expeditions in early April, whereas in 2024 repeated collections were required until mid-May because of markedly low capture success. We therefore examined whether this difference was associated with unusual environmental conditions and whether FA was higher in 2024, as expected under greater developmental perturbation. Daily temperature and relative humidity were examined from early March onward, encompassing approximately one month before adult emergence. The 2024 sampling period was warmer and drier than the corresponding periods in 2022 and 2026 and coincided with the final phase of the strong 2023-2024 El Ni&ntildeo event. Contrary to our prediction, FA was significantly lower in 2024. The magnitude of directional asymmetry remained similar among years, although the spatial pattern of the DA vector differed between 2024 and 2026. The coincidence of reduced capture success and reduced FA is consistent with the hypothesis that adverse conditions may impose demographic filtering, such that individuals expressing greater developmental instability are less likely to contribute to the sampled adult population.

Agricultural intensification is a major cause of population declines in farmland birds and insects worldwide. While these declines are expected to disrupt trophic interactions through density-dependent cascading effects, examples outside of crop pest control or involving more than two trophic levels remain poorly documented. Here we quantify such cascading effects across three trophic levels involving a declining aerial insectivore, the Tree Swallow (Tachycineta bicolor), which breeding success decreases with agricultural intensity, Protocalliphora bird blowflies (Diptera: Calliphoridae) that parasitize its nestlings, and Nasonia parasitoid jewel wasps (Hymenoptera: Pteromalidae) that feed upon blowfly pupae within swallow nests. Agriculture intensity may affect each of these actors either directly via, for instance, toxicological effects from pesticide use, or indirectly through density-dependent trophic interactions, which can exacerbate or mitigate one another. Using Bayesian models within a causal inference framework, we quantified how nestling host density, meteorological conditions, and agricultural landscape context affect Nasonia parasitoid infestation of Protocalliphora pupae, and estimated Protocalliphora emergence success. Analyses were based on 3,340 Protocalliphora puparia collected from 248 Tree Swallow nests over a 16-year period (2004-2019) across a 10,200-km2 agricultural intensity gradient in Southern Quebec, Canada. Model predictions indicated that Protocalliphora emergence probability increased steeply with nestling host availability (i.e., nestling-days). Whereas Nasonia parasitoid infestation occurrence at the nest level increased with Protocalliphora host availability, the proportion of infested Protocalliphora pupae within nest decreased and led to a dilution effect at the individual level. Although Protocalliphora abundance within nests decreased with agricultural intensity, their emergence probability peaked in agrointensive landscapes. This increase was associated with reduced Nasonia infestation rates, suggesting that agricultural intensity indirectly mitigated parasitoid pressure on Protocalliphora host populations. Our results highlight how agricultural intensification can shape multitrophic interactions and life-history traits (emergence success and infestation rates) by simultaneously reducing host availability and weakening top-down control by parasitoids.

Stink bugs (Hemiptera Pentatomidae) are major agricultural pests worldwide, including both native and invasive species. In France, for instance, Halyomorpha halys has rapidly expanded its range, affecting key crops such as hazelnuts, apples, and vegetables. Meanwhile, several native, polyphagous species - Nezara viridula, Palomena prasina and, to a lesser extent, Graphosoma italicum - are re-emerging and impacting diverse crops because of changes in agricultural practices and climatic conditions. Egg parasitoids represent promising biological control agents for these pests, be it through conservation, augmentation or introduction biological control. However, their actual potential is not precisely documented due to a lack of ambitious surveys and possible taxonomic issues. This study aims to address this gap by compiling results obtained from various of egg parasitism surveys of Pentatomidae in France and implementing a large-scale DNA Barcoding approach (2000 individuals) for the emerged parasitoids. Our results indicate a high diversity of egg parasitoids, and detected some taxonomic issues and molecular inconsistencies that warrant further study. Among the three families of egg parasitoids recovered (Encyrtidae, Eupelmide, and Scelionidae), Scelionidae was the most abundant and diverse with nine species of Trissolcus (including the two adventive species, Tr. japonicus and Tr. mitsukurii) and four Telenomus species (including two unidentified to species). Scelionidae dominated the parasitoid assemblages associated with most of the Pentatomidae host species, except for H. halys for which the eupelmid Anastatus bifasciatus was the most common species.

BACKGROUND: The Argentine ant (Linepithema humile) is among the world's worst invasive species. In the Donana Biological Reserve (Spain), it is associated with human structures that provide the mild, moist conditions it needs within the hot, dry scrubland. We evaluated a habitat-modification treatment, predicting that removing this suitable habitat would eradicate the invader locally. Over an 18-year period, we monitored ant communities at a treated and an untreated site, at different distances from the human structures, before and after treatment, and analysed how temperature and worker numbers affected encounters at baits between the Argentine ant and native ants. RESULTS: Distance to the human structures shaped ant communities at both sites, but only the treated site changed after treatment. There, the Argentine ant decreased close to the human structure and almost disappeared farther from it, whereas the endemic Cataglyphis tartessica and C. floricola recovered, especially close to the structure. At baits, the outcome of encounters depended mainly on how temperature changes favoured each species relative to its maximum activity temperature: Cataglyphis spp. displaced the Argentine ant in the morning, as temperature increased, and the Argentine ant recovered the baits in the late afternoon. Numerical advantage favoured only the Argentine ant. CONCLUSION: Habitat modification reduced the Argentine ant and allowed endemic ants to recover, but did not eradicate the invader, which persisted at low abundance 13 years after treatment. In protected areas, habitat management should be combined with eradication, monitoring and prevention of spread.

Immune defenses may vary across environments due to differences in life history or abiotic and biotic characteristics, but few studies have compared the strength of immune responses across broad geographical gradients. Here we investigated how bacteria killing ability (BKA), a measure of constitutive innate immune function, varies among populations of tree swallows (Tachycineta bicolor) inhabiting different environments. We hypothesized that populations living in unpredictable environments, which also have shorter breeding seasons and thus fewer opportunities to renest in the event of reproductive failure, would invest in reproduction at the expense of immunity. To test this hypothesis, we measured BKA and monitored reproductive activity in four populations located across most of the breeding range of tree swallows, in Tennessee, New York, Wyoming and Alaska. Consistent with our predictions, BKA was lowest in Alaska and Wyoming and highest in Tennessee. In most populations BKA was also lower during incubation than during nestling provisioning, and lower in males than in females. These results suggest that the high reproductive investment seen in populations experiencing more unpredictable breeding conditions may come at a cost to immune function. While reduced immune investment could increase susceptibility to parasites, this potential cost is likely offset by lower parasite pressure in these environments, limiting the need for maintaining strong constitutive innate defenses like BKA.

Defended prey are often thought to rely on conspicuous warning signals to distinguish themselves from undefended prey, facilitating predator learning and avoidance. Yet many chemically defended organisms are inconspicuous and difficult to distinguish from palatable prey, raising a fundamental question: how do predators avoid defended prey when prey themselves provide little or no reliable signals of defense? We tested whether host plants can function as indirect indicators of prey defense using Carolina wrens (Thryothorus ludovicianus), chemically defended Eumaeus atala larvae, undefended Galleria mellonella larvae, and two distinct plant species. Defended and undefended prey were experimentally made to appear visually identical, forcing predators to rely on host-plant associations as the only available source of information. Wrens rapidly altered both search behavior and attack decisions according to plant identity. Mechanistic attack models incorporating predator discrimination between defended and undefended prey were strongly favored when plants were present, with defended prey experiencing substantially lower attack risk than undefended prey. When plants were removed, support for discrimination weakened and attacks on both prey types increased. Spatial autocorrelation of host plants further shaped predator behavior, with strongly clustered plants hosting defended prey receiving disproportionately fewer visits. Together, these results suggest host plants can function as ecologically meaningful cues of prey defense, influencing both predator search patterns and attack decisions. More broadly, our findings suggest warning systems may extend beyond prey phenotype alone, and that ecological context (including host-plant identity and spatial structure) may contribute to the evolution and maintenance of aposematism.

Fruit resource availability can influence the local abundance of avian frugivores through bottom-up regulation, but whether greater resource availability translates into higher visitation rates to fruiting trees remains poorly understood. Greater fruit availability could increase visitation by supporting larger frugivore populations, or reduce visitation to individual trees if increases in frugivore abundance are not proportionate to those in fruit availability or if frugivores distribute their foraging effort. Understanding these relationships can provide insights into the relative role of abundance and trait-based mechanisms in structuring plant-frugivore communities. We compared fruit availability, avian frugivore abundance, and frugivore visitation rates on fruiting trees across two protected wet tropical forest sites: Anamalai Tiger Reserve in the Western Ghats and Namdapha Tiger Reserve in the Eastern Himalaya. Specifically, we quantified the availability of bird-consumed fruits across one-ha patches, estimated local abundances of major frugivore groups, and tested whether visitation rates on individual fruiting trees were related to frugivore abundance, body mass, and degree of frugivory. We found that small-seeded fruit availability was significantly higher in Anamalai than in Namdapha. Local abundances of several relatively small-bodied frugivore groups, including bulbuls, barbets, fairy-bluebirds, and mynas, were also higher in Anamalai. However, visitation rates of several frugivore groups on individual fruiting trees were higher in Namdapha. Visitation rates across all avian frugivore species were associated with frugivore abundances only in Anamalai, and not associated with body mass or degree of frugivory in either site. Thus, although greater fruit availability was likely associated with higher frugivore abundance, this increase in abundance did not consistently translate into higher visitation rates at individual fruiting trees, which provides some support for the resource dilution hypothesis. Our results highlight the importance of considering fruit resource availability and frugivore abundance when examining variation in tropical plant-frugivore interactions.

Aims In forest ecosystems, tree species composition and diversity are fundamental drivers of biodiversity and many species are closely associated to specific tree species as hosts. Saproxylic diversity across tree species may be shaped by interactions between ecological and environmental factors, such as resource availability. However, a throughout and unbiased quantification of diversity across tree species is missing. We investigated patterns an drivers of saproxylic beetle diversity across European tree genera while accounting for differences in sampling effort. Location Europe Methods We used a large dataset, of 25 studies, comprising 500,000 deadwood-dependent beetles, representing 1041 saproxylic beetle species, sampled from 29 tree genera. We accounted for sampling effort by estimating diversity using coverage-based standardization across Hill numbers. We than used linear models to identify drivers of saproxylic beetle diversity across tree genera and assessed differences in community composition using Nonmetric Multidimensional Scaling (NMDS). Additionally, the most abundant beetle families were identified for a subset of 14 genera. Results Quercus supported the highest richness of infrequent, frequent, and highly frequent species, while Fagus exhibited the highest observed (unstandardized) species richness. Beetle communities were less differentiated when focusing on infrequent species, whereas tree genera were separated when focusing on frequent and highly frequent species. In addition, we found that resource availability and maximum tree height best predicted infrequent beetle diversity, whereas resource availability was the main driver of frequent species. In contrast, the same analyses for unstandardized data indicated postglacial occurrence as an important factor for infrequent species. Main conclusions Although resource availability supported the species area hypothesis, standardized data revealed higher richness on smaller trees, partly contradicting this pattern. Our results highlight the importance of accounting for sampling bias and promoting tree diversity, particularly oaks, to sustain saproxylic beetle diversity.

The toxicity of chemical defences is well studied, but the potential contribution of compound structure to predator deterrence remains largely unexplored. Whether predation acts more strongly on toxicity or unpalatability remains largely untested, partly because few systems allow toxin structure to vary independently of quantity. Heliconius sara larvae provide such a system: those reared on Passiflora auriculata sequester cyclopentenyl cyanogenic glucosides (CGs), while those reared on P. biflora biosynthesise comparable quantities of aliphatic CGs. Using two invertebrate predators, Camponotus floridanus ants and Hierodula membranacea mantids, we tested whether this structural difference affects palatability independent of toxicity. Mantids rejected larvae with cyclopentenyl CGs more often than larvae with aliphatic CGs, despite no detectable difference in total CG content. This pattern was mirrored in extract-based assays with ants, independently of cyanide release: extracts with cyclopentenyl CGs remained deterrent, while extracts with aliphatic CGs did not differ in deterrence from water. Live larvae, by contrast, elicited similar responses from ants regardless of CG structure. These results show that variation in toxin structure can strongly affect palatability, with some compounds conferring greater protection than others. This demonstrates the importance of chemical structural diversity in the evolution of chemical defences.

Anticipating and managing the impact of herbivorous pests requires evidence-based knowledge about the interactions between pests and their natural enemies. Knowledge of species' ecologies and biological interactions are typically disseminated in unstructured text across hundreds of thousands of scientific articles spanning a rapidly growing scientific literature, but manually screening this literature is time-consuming and impractical at scale. Taxonomic and geographic coverage thus remains sparse, and structured data on interactions between individual species are lacking, particularly for invertebrates. Large language models (LLMs) have recently emerged as a novel and powerful text-mining tool for knowledge extraction and evidence synthesis in a wide range of scientific disciplines, including ecology and conservation. In this study, we use an open-weight, pre-trained LLM to analyse abstracts of a corpus of published material on biological pest control to obtain a global Database of Pest Herbivores and their Natural Enemies (DAPHNE). This method resulted in the extraction of 175,404 species interactions from 112,830 published pest control studies, containing16,755 unique animal taxa resolved at the species level. Interactions include herbivory (granivory, frugivory and gall-formation), predation, parasitism and hyperparasitism, and comprise a range of additional information, such as species' taxonomy, pest status, pest importance, natural enemy importance, provision of biocontrol, associated plants and industries, invasiveness and the vectoring of pathogens and diseases. Validation of the results shows that most data columns were extracted with high recall and precision (>90%) and comparison of DAPHNE with other sources shows a high degree of agreement, but also highlights that the dataset contains information that may have been missed by other sources. In addition to the identification of important crop pests and their natural enemies, DAPHNE may be used for a variety of use-cases, including the identification of invasive species and pathogen vectors, trophic network analysis and literature search and discovery.

Developing in suboptimal temperatures can have widespread negative effects in organisms, but early exposure to thermal challenges can also trigger increased investment in thermoregulatory capacity. Within birds, the effects of cold exposure during incubation may differ between precocial and altricial species due to differences in the ontogeny of thermoregulation. To date, most of the evidence showing that embryonic cold exposure shapes future thermoregulatory capacity comes from a few precocial species in laboratory settings. Less is known about sensitivity to low-temperature incubation in altricial species which only become fully endothermic after hatching. In this study, we tested the effects of cold temperatures during embryonic development by temporarily cooling the nest boxes of free-living tree swallows (Tachycineta bicolor) during late incubation and subsequently exposing nestlings to an acute cold challenge. Cold exposure during early development made nestlings better at maintaining their body temperatures during the acute challenge. Developmentally cold-exposed birds also had higher thyroxine (T4) levels when sampled at lower ambient temperatures, whereas control birds showed the opposite relationship. Among nestlings that failed to maintain their body temperature during the acute cold challenge, developmentally cold-exposed nestlings secreted more corticosterone during the acute cold challenge than control nestlings. Despite these changes, cold-exposed birds did not differ from controls in cold-induced metabolic rates, body mass, or bacteria killing ability. These results are, to our knowledge, the first to show that developmental cold exposure increases the capacity to maintain body temperature during future cold challenges in a songbird. These findings suggest that experiencing even a mild decline in ambient temperatures during embryonic development could prime birds to cope more effectively with harsh or variable environmental conditions later in life.

1. Assessing the conservation value of secondary forests and reforestation is important for conservation planning. Butterflies are widely used as indicators, and fruit-feeding butterflies are often used in biodiversity assessments in tropical landscapes. 2. We examined fruit-feeding butterfly diversity, abundance, and community composition across a primary forest, a secondary forest, and a plantation forest in northern Vietnam. We sampled butterflies nearly monthly during one year using baited traps. 3. Primary and secondary forest supported higher species richness than plantation forest. Moreover, while secondary forest had mainly a subset of species found in primary forest, the plantation forest had a distinct butterfly fauna. 4. Butterfly abundance and community composition varied across months, without showing a clear seasonal pattern. 5. Our results suggest that secondary and plantation forests do not fully replace primary forests, but they contribute meaningfully to butterfly conservation in human-modified tropical landscapes.

Coinfections are common in a nature and often involve competition among coinfecting parasites to extract resources from the host. As a consequence of this competition, parasites can face trade-offs between investing in competition with other parasites and exploiting the host for their own growth and transmission. Such within-host interactions among parasites can either increase or decrease virulence depending on how they alter parasite density, resource use, and host damage. We tested the inhibitory effect of different species of the entomopathogenic fungus Metarhizium on one another in vitro and the impact of coinfection on virulence towards Tribolium castaneum. We found that Metarhizium pemphigi is able to inhibit all other isolates of Metarhizium tested, whereas Metarhizium pingshaense was relatively resistant to inhibition by other Metarhizium strains. Virulence towards the host, Tribolium castaneum, differed very little among isolates tested. We did, however, observe differences between virulence in single and coinfections in two cases. Where there were virulence differences, these were both consistent with in vitro inhibition patterns and interestingly resulted in reduced virulence in coinfection. This is inconsistent with broader patterns of virulence in coinfection, where virulence seems to be driven by the more virulent parasite. It is, however, consistent with data from other systems where there is evidence of interference competition. Our data thus support the idea that, in contrast to other forms of between parasite interaction, interference competition results in reduced virulence in coinfection.