Sex ratios are an important component of parasitoid wasps' reproductive strategies and seem to be generally well described by evolutionary ecological theory, such as local mate competition (LMC). The sex ratios of several Sclerodermus species do not fit the predictions of standard LMC models, as their sex ratios remain strongly female biased irrespective of the number of foundress females contributing offspring to locally mating groups. Unusually among parasitoids, Sclerodermus are quasi-social: co-foundresses remaining in association with each other for long periods while communally producing and tending large broods of offspring on a single host. Modified LMC theory, considering that some co-foundresses may actively alter the sex ratios produced by other co-foundresses via physiological suppression or post-ovipositional infanticide, predicts that brood sex ratios at maturity will be relatively insensitive to foundress number, as observed within species. Here, we explore whether the within-species and with-study sex ratio patterns are also observed across studies and species, using data from 38 prior studies in a comparative analysis of the relationship between sex ratio and foundress number. We find that, like within-species observations, sex ratios increase very only mildly, or not at all, as foundress numbers increase, and are only slightly affected by host species and by wasp species identity: Sclerodermus brood sex ratios essentially remain at around 9% males. Current theory and current evidence are broadly akin but do not match exactly: This may be due to methodological constraints in our comparative analyses or to unexplored or unmodelled aspects of the biology of Sclerodermus.

The coffee berry borer (CBB, Hypothenemus hampei) is the most destructive pest of coffee, causing significant economic consequences in an array of coffee-producing regions, including Puerto Rico. Following the implementation of biological control programs using the parasitoid wasp Cephalonomia stephanoderis, key questions remain regarding how laboratory-reared wasps compare to field wasps in retaining beneficial traits, such as foraging, host attack, and offspring production. It is also of interest whether laboratory and field populations differ in the microbiota they harbor, as microbial communities can directly influence insect performance. Making these comparisons, we find that core natural-enemy functions remain largely intact in laboratory-reared wasps, but that small differences exist between these and field-collected wasps in terms of host-stage preference and oviposition timing. We also find substantial differences in microbial composition between field-collected wasps and those reared in the laboratory. Field-collected parasitoids harbored a simple microbial profile dominated by the Actinomycetota, a diverse phylum of Gram-positive bacteria, particularly in the family Corynebacterium, while laboratory-reared wasps exhibited higher diversity involving a broader range of bacterial phyla. These microbiome differences, confirmed by alpha and beta diversity analyses, suggest that laboratory rearing restructures parasitoid-associated microbial communities. While behavioral performance remained largely comparable, differences in microbial community composition suggest that microbiota should be considered when evaluating laboratory-reared agents for pest management programs. Further studies are needed to better understand microbial shifts and their potential links to parasitoid behavior and performance.

American cranberry (Vaccinium macrocarpon) is a native North American fruit crop, cultivated mainly in a small number of countries, including the USA, Canada, Chile in the New World, and Türkiye, Germany, Belarus, Poland and Sweden in Eurasia. In Finland, experimental and commercial cultivation of American cranberries has recently been initiated, developing new technology for soilless table-top cultivation in high plastic tunnels. Here we report, for the first time, that Aphis fabae, a polyphagous aphid and eight species of lepidopterans (moth larvae) feed on American cranberry plants in Finland. Six species of lepidopterans belong to the family Noctuidae (Lacanobia contigua, Lacanobia oleracea, Xestia baja, Anarta trifolii, Xanthia togata and Amphipyra pyramidea) and two species to the family Geometridae (Biston betularia and Hypomecis roboraria). These insects may become pests of economic importance to Finnish producers. All insects reported in this study have established populations in Finland, feeding on many deciduous trees and herbaceous grasses. The proximity of landscapes containing such plants might have influenced the migration of these insects into the cranberry crop.

1. More and more data on species traits are being collected and made openly available. Despite these efforts, effective syntheses of trait data to comprehend how species respond to and affect their environment are hampered by inadequate standards for publishing the data and the associated metadata, which limits the interoperability and reuse of data across studies. 2. We have developed ShareTrait (https://sharetrait.org/), a novel initiative that consolidates individual-level trait data and associated metadata in an interoperable and reusable format, enabling standardised and integrated use. As a proof-of-concept, we initially focus on three core traits of ectotherms: metabolic rate, development time and fecundity. These traits, measurable in almost all animals, are fundamental to an organism's overall fitness. 3. ShareTrait enables researchers to share their (meta)data with the research community. To date, researchers from diverse fields have contributed 28,692 individual-level data records to ShareTrait. These records originated from 45 datasets and are just the tip of the iceberg of existing data, highlighting the potential of ShareTrait to be a valuable community resource for meta-analyses and comparative approaches. 4. Future directions of ShareTrait will focus on accumulating more records, expanding to cover more traits, including those measurable at the population level, and partnering with journals in relevant fields (ecology, physiology, evolution) to make sharing standardised trait data part of the standard publication process. 5. We envision ShareTrait, along with its digital infrastructure and comprehensive metadata, to be a catalyst for collating trait data across species. ShareTrait can streamline research efforts, minimise duplication and empower researchers to explore patterns and broader ecological, evolutionary and physiological questions among taxa (e.g. via meta-analyses and comparative approaches). This way, ShareTrait will unlock new frontiers in trait-based approaches, enhancing our understanding of species-environment relationships.Read the free for this article on the Journal blog.

Biological pest control programmes often involve the importation of exotic natural enemies, ideally followed by monitoring to discern the establishment and success of the programme. Several species of egg parasitoids in the genus Trichogramma have been released against the pomegranate butterfly, Deudorix livia, in Oman annually for nearly two decades. We estimated agri-field parasitism by Trichogramma wasps and conclude that these parasitoids are almost completely ineffective. Parasitoid emergence from D. livia eggs was almost exclusively by the naturally present wasp Telenomus nizwaensis, but this species typically achieves parasitism too late in the fruiting season to prevent economic damage. We suggest that a more targeted selection of Trichogramma species and strains is used in conjunction with improved mass-rearing or, alternatively, that active attempts to utilise Trichogramma as exotic natural enemies cease. We recommend that resources are allocated to improving parasitism, in terms of the timing and prevalence, achieved by the indigenous egg parasitoid.

The composition and dynamics of ecological communities are complex because of the presence of large numbers of organisms, belonging to many different species, each with their own evolutionary history, and their numerous interactions. The construction and analysis of trophic webs summarizes interactions across trophic levels and links community structure to properties such as ecosystem services. We focus on agro-ecological communities, which may be simpler than natural communities but nonetheless present considerable challenges to describe and understand. We review the characteristics and study of communities comprised of plants, phytophagous insects and insect parasitoids with particular regard to the maintenance of sustainable agro-ecological communities and ecosystem services, especially biological pest control. We are constrained to largely overlook other members of these communities, such as hyper-parasitoids, predators, parasites and microbes. We draw chiefly on recent literature while acknowledging the importance of many advances made during the immediately preceding decades. Trophic web construction and analysis can greatly improve the understanding of the role and impact of herbivores and natural enemies in agro-ecological communities and the various species interactions, such as apparent competition, which assists biocontrol strategies. The study of trophic webs also helps in predicting community ecology consequences of externally-driven changes to agro-ecosystems.

The release of biological control agents has been an important means of controlling invasive species for over 150 years. While these releases have led to the sustainable control of over 250 invasive pest and weed species worldwide, a minority have caused environmental harm. A growing recognition of the risks of biological control led to a focus on risk assessment beginning in the 1990s along with a precipitous decline in releases. While this new focus greatly improved the safety of biological control, it came at the cost of lost opportunities to solve environmental problems associated with invasive species. A framework that incorporates benefits and risks of biological control is thus needed to understand the net environmental effects of biological control releases. We introduce such a framework, using native biodiversity as the common currency for both benefits and risks. The model is based on interactions among four categories of organisms: (1) the biological control agent, (2) the invasive species (pest or weed) targeted by the agent, (3) one or more native species that stand to benefit from the control of the target species, and (4) one or more native species that are at risk of being harmed by the released biological control agent. Conservation values of the potentially benefited and harmed native species are incorporated as well, and they are weighted according to three axes: vulnerability to extinction, the ecosystem services provided, and cultural significance. Further, we incorporate the potential for indirect risks to native species, which we consider will result mainly from the ecological process of agent enrichment that may occur if the agent exploits but does not control the target pest or weed. We illustrate the use of this framework by retrospectively analyzing the release of the vedalia beetle, Novius (= Rodolia) cardinalis, to control the cottony cushion scale, Icerya purchasi, in the Galapagos Islands. While the framework is particularly adaptable to biological control releases in natural areas, it can also be used in managed settings, where biological control protects native species through the reduction of pesticide use.

Exotic natural enemies that are imported to control a target pest may attack non-target species or disrupt the performance of other natural enemies of the target that are already present. We evaluate possible interactions between three parasitoid species, the native Telenomus nizwaensis and the imported Trichogramma brassicae and Trichogramma evanescens, when presented with Deudorix livia host eggs under high-density laboratory conditions. Deudorix livia is a butterfly which is an economically damaging pest in the Omani pomegranate agro-ecosystem. Most (73.5% overall) of the observed parasitism was by T. nizwaensis. It performed best when presented with host eggs in the absence of either of the Trichogramma species. These imported species thus have some potential to disrupt suppression of the pest by the indigenous natural enemy under lower-density conditions in the field, and neither of them achieved high parasitism rates themselves (laboratory conditions: T. brassicae = 12.5%; T. evanescens = 18.5%; with no evidence for any parasitism of field-collected eggs). Future efforts in this agro-ecosystem would best be directed towards encouraging T. nizwaensis, rather than towards importation of Trichogramma. Screening for negative effects of natural enemies on the pest suppression provided by other natural enemies is recommended.

Many parasitoids alter their reproductive behaviour in response to the quality of encountered hosts. They make adaptive decisions concerning whether to parasitise a potential host, the number of eggs laid on an accepted host, and the allocation of sex to their offspring. Here we present evidence that Goniozus jacintae Farrugia (Hymenoptera: Bethylidae), a gregarious ectoparasitoid of larval tortricids, adjusts its reproductive response to the size and developmental stage of larvae of the light brown apple moth (LBAM), Epiphyas postvittana (Walker) (Lepidoptera: Tortricidae). Goniozus jacintae parasitises instars 3-6 of LBAM, but most readily parasitises the later, larger, instars. Brood sizes were bigger on larger hosts and brood sex ratios were female biased (proportion of males = 0.23) with extremely low variance (never >1 male in a brood at emergence), perhaps the most precise of all studied bethylids. Host size did not influence brood development time, which averaged 19.64 days, or the body size of male offspring. However, the size of females was positively correlated with host size and negatively correlated with brood size. The sizes of individual males and females were positively related to the average amount of host resource available to individuals within each brood, suggesting that adult body size is affected by scramble competition among feeding larvae. Average brood sizes were: 3rd instar host, 1.3 (SE +/- 0.075); 4th instar, 2.8 (SE +/- 0.18); 5th instar, 4.7 (SE +/- 0.23); 6th instar, 5.4 (SE +/- 0.28). The largest brood size observed was 8 individuals (7 females, 1 male) on the 6th instar of LBAM. These results suggest that later instars would give the highest yield to optimise mass-rearing of G. jacintae if used for augmentative biological pest control.

Understanding the composition and dynamics of ecological communities is challenging because of the large number of organisms present and their numerous interactions. Among agricultural systems, intercropping considerably increases the complexity of communities compared to monocultures and alternative host plants can influence insect pest damage. Using literature records, we construct and analyse connectance trophic webs of date palm ( Phoenix dactylifera ) agro-ecosystems, including and excluding intercrops. Estimates of connectance (community complexity) are relatively low and little affected by consideration of intercrops. Plant–herbivore overlap is relatively high, suggesting that herbivores are typically not specialists. Herbivore–natural enemy overlap is greater when intercrops are considered, suggesting that diffuse apparent competition regulates pest populations. We pay particular attention to how trophic web structure might affect Batrachedra amydraula (Lesser date moth), an important economic pest. Records indicate it having 15 species of natural enemies and sharing 9 of these with other herbivores; these may maintain populations of natural enemies when the moth is seasonally rare, contributing to pest suppression. The estimated potential for apparent competition between the lesser date moth and other herbivores is higher when intercrops are considered. The consequent expectation of less severe infestations in plantations that are intercropped compared to monocultures matches empirically derived reports. Further, comparing results obtained from the literature on one country (Oman) and from 15 Middle Eastern countries, we find that community metric estimates are relatively little affected by the geographical scale considered. Overall, our results suggest that literature-based trophic web construction can provide an efficient and robust alternative, or in addition, to direct empirical methodologies and that the presence of intercrops will contribute to major pest suppression via indirect apparent competition.

Mitochondria are intracellular organelles responsible for cellular respiration with one of their major roles in the production of energy in the form of ATP. Activities with increased energetic demand are especially dependent on efficient ATP production, hence sufficient mitochondrial function is fundamental. In bees, flight muscle and the brain have particularly high densities of mitochondria to facilitate the substantial ATP production required for flight activity and neuronal signalling. Neonicotinoids are systemic synthetic insecticides that are widely utilised against crop herbivores but have been reported to cause, by unknown mechanisms, mitochondrial dysfunction, decreasing cognitive function and flight activity among pollinating bees. Here we explore, using high-resolution respirometry, how the neonicotinoid imidacloprid may affect oxidative phosphorylation in the brain and flight muscle of the buff-tailed bumblebee, Bombus terrestris. We find that acute exposure increases routine oxygen consumption in the flight muscle of worker bees. This provides a candidate explanation for prior reports of early declines in flight activity following acute exposure. We further find that imidacloprid increases the maximum electron transport capacity in the brain, with a trend towards increased overall oxygen consumption. However, intra-individual variability is high, limiting the extent to which apparent effects of imidacloprid on brain mitochondria are shown conclusively. Overall, our results highlight the necessity to examine tissue-specific effects of imidacloprid on respiration and energy production.

For most foraging parasitoids, it is disadvantageous to share a host. In the genus Sclerodermus females can benefit from being among groups of foundresses, which cooperate in brood production over several weeks, but intra-group conflicts also arise. We provided groups of females, with varying degrees of relatedness, with two hosts, in varying host size combinations, and observed behaviours and performance. Foundress death, likely caused by host defensive behaviour, was common during the initial phase, especially when foundresses were closer kin. At least one host was always oviposited on and in 60% of cases both were. When host size differed and only one was oviposited on, there was no preference for larger hosts. Oviposition was most rapid when both hosts were large and females were non-siblings. Offspring production was greatest when broods developed on two large hosts and was not influenced by foundress kinship. Aggregation of foundresses across hosts may be promoted by variation in host size and by kinship. Foundresses were most commonly observed alone on a host but also shared hosts; all females on a single host was uncommon. Foundresses commonly moved between the hosts, most frequently when both hosts were large. Movement was not, overall, influenced by kinship. Overall, the behavioural repertoire of Sclerodermus indicates that they are able to assess and exploit locally available alternative reproductive opportunities and may attune some of their decisions according to inter-group relatedness.

Many parasitoids alter their reproductive behaviour in response to the quality of encountered hosts. They make adaptive decisions concerning whether to parasitise a potential host, the number of eggs laid on an accepted host, and the allocation of sex to their offspring. Here we present evidence that

A new species of bethylid parasitoid wasp, Goniozus omanensis Polaszek sp. n., is described based on morphology and DNA sequence data. The species is currently known only from the lesser date moth Batrachedra amydraula, a pest of economic importance, but can be reared on two factitious host species. G. omanensis is compared with G. swirskiana, known from the same host in Israel. We summarise current knowledge of G. omanensis life-history, and its potential as an agent of biological pest control.

In many African countries, anthropogenic pressure and poor governance have led to the degradation of wildlife corridors, which are important for the long-term viability of wildlife populations. Yet the nature of such degradation is poorly understood, hindering our ability to reverse these trends. We studied a deteriorating wildlife corridor between Katavi and Mahale National Parks in western Tanzania. Using satellite imagery, we found that the corridor still contains large areas of natural vegetation, diverse terrain and numerous water sources. There has nonetheless been increasing encroachment of the corridor by people between 1990 and 2017, exemplified by a 9% reduction in the area covered by miombo woodlands and a fourfold increase in the area covered by settlements and agricultural land. We used three additional methods to assess deterioration over the last three decades: elephants' movement routes, peoples' perception of animal populations and incidents of human-wildlife conflicts. Elephants were primarily found only in the parts of the corridor adjacent to the two national parks. Tracking of elephant spoor revealed a much-diminished corridor use, suggesting that seemingly 'healthy' habitat within a wildlife corridor will not necessarily predict the presence of elephants or perhaps of other species. Other factors particularly the increasing presence of humans in the area are possibly more important for predicting elephant use of a corridor. Interviews with local residents and conservation experts suggested that, although use by some animal species has declined, many ungulates were still seen in the corridor and neighbouring villages, some of which were associated with human-wildlife conflict. All villages around the corridor were affected by the human-wildlife conflict; this comprised crop damage, livestock injury or killing and attacks on humans. We conclude that corridors could be restored if people were restricted from settling, but this would require governments to enact policies that balance the conservation of Natural Capital with survival of human populations; the latter may involve internal migration in response to growing population pressures. Dans de nombreux pays africains, la pression anthropique et la mauvaise gouvernance ont entra & icirc;n & eacute; la d & eacute;gradation des corridors de faune, qui sont importants pour la viabilit & eacute; & agrave; long terme des populations d'animaux sauvages. Pourtant, la nature de cette d & eacute;gradation est mal comprise, ce qui entrave notre capacit & eacute; & agrave; inverser ces tendances. Nous avons & eacute;tudi & eacute; un corridor de faune en cours de d & eacute;t & eacute;rioration entre les parcs nationaux de Katavi et de Mahale, dans l'ouest de la Tanzanie. Gr & acirc;ce & agrave; l'imagerie satellitaire, nous avons constat & eacute; que le corridor contient encore de vastes zones de v & eacute;g & eacute;tation naturelle, un terrain vari & eacute; et de nombreuses sources d'eau. N & eacute;anmoins, entre 1990 et 2017, l'empi & egrave;tement des populations sur le corridor s'est accru, comme en t & eacute;moignent la r & eacute;duction de 9% de la superficie couverte par les for & ecirc;ts de miombo et la multiplication par quatre de la superficie couverte par les zones d'habitation et les terres agricoles. Nous avons utilis & eacute; trois m & eacute;thodes suppl & eacute;mentaires pour & eacute;valuer la d & eacute;t & eacute;rioration au cours des trois derni & egrave;res d & eacute;cennies : les itin & eacute;raires de d & eacute;placement des & eacute;l & eacute;phants, la perception qu'ont les gens des populations animales et les incidents li & eacute;s aux conflits entre l'homme et la faune. Les & eacute;l & eacute;phants ne se trouvaient principalement que dans les parties du corridor adjacentes aux deux parcs nationaux. Le suivi des traces d'& eacute;l & eacute;phants a r & eacute;v & eacute;l & eacute; une utilisation tr & egrave;s r & eacute;duite du corridor, ce qui sugg & egrave;re qu'un habitat apparemment << sain >> au sein d'un corridor de faune ne permet pas n & eacute;cessairement de pr & eacute;dire la pr & eacute;sence d'& eacute;l & eacute;phants ou peut-& ecirc;tre d'autres esp & egrave;ces. D'autres facteurs, en particulier la pr & eacute;sence croissante de l'homme dans la r & eacute;gion, sont peut-& ecirc;tre plus importants pour pr & eacute;dire l'utilisation d'un corridor par les & eacute;l & eacute;phants. Les entretiens avec les r & eacute;sidents locaux et les experts en conservation ont sugg & eacute;r & eacute; que, bien que l'utilisation par certaines esp & egrave;ces animales ait diminu & eacute;, de nombreux ongul & eacute;s & eacute;taient encore observ & eacute;s dans le corridor et les villages voisins, certains d'entre eux & eacute;tant associ & eacute;s & agrave; des conflits entre l'homme et la faune. Tous les villages situ & eacute;s autour du corridor ont & eacute;t & eacute; touch & eacute;s par le conflit entre l'homme et la faune, qui s'est traduit par des dommages aux cultures, des blessures ou des abattages de b & eacute;tail et des attaques contre l'homme. Nous concluons que les corridors pourraient & ecirc;tre restaur & eacute;s si l'on emp & ecirc;chait les gens de s'installer, mais il faudrait pour cela que les gouvernements adoptent des politiques & eacute;quilibrant la conservation du capital naturel et la survie des populations humaines ; cette derni & egrave;re peut impliquer des migrations internes en r & eacute;ponse aux pressions d & eacute;mographiques croissantes.

One of the key decisions made by parents is determining how many offspring to produce using the available resources. This decision is often made in the presence of other individuals that are also attempting to reproduce. Here, we explored the clutch size response of group-reproducing female parasitoids in the bethylid genus Sclerodermus to the presence of their conspecifics prior to oviposition. We removed excess foundresses before oviposition and focused on the subsequent decisions of individual foundresses. We tested two hypotheses regarding the cues that foundresses may use to attune their reproduction. One was that clutch size decisions are adjusted according to the host handling stage at which cofoundress groups form prior to oviposition. We found no support for this hypothesis, possibly because our experimental groups were unnaturally brief. The other was that cofoundresses assess the time they are together with the host prior to oviposition to adjust their clutch size decisions. We found support for this hypothesis via a decline in the size of clutches produced by individual foundresses as the duration of their association with cofoundresses increased. It appears that smaller clutches were laid in anticipation of concurrent reproduction by the associated cofoundresses and to maintain sufficient per capita resources for the development of offspring that will experience scramble competition. This explanation was supported by further findings that larger offspring were produced when the association with cofoundresses was for longer periods. In Sclerodermus, lengthy associations with cofoundresses, both pre- and postoviposition, mean that the clutch size decisions in this study are just part of a wider set of strategic considerations that affect the success of any given foundress and her offspring within the reproductive group. (c) 2024 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights are reserved, including those for text and data mining, AI training, and similar technologies.

In nature, multiple parasitoid species often attempt to exploit the same stages of a given host species, leading to competitive interactions amongst them. These interspecific interactions can influence the size and composition of ecological communities. Some parasitoids can identify whether an encountered host has already been parasitised by another species, termed host discrimination, and may choose to reject or accept it (acceptance is termed multiparasitism). The host discrimination ability of a parasitoid that could potentially serve as a biological control agent may contribute to its efficacy in suppressing target pest populations. Female Goniozus jacintae Farrugia (Hymenoptera: Bethylidae), an ectoparasitoid, were tested for their ability to discriminate between unparasitised light brown apple moth (LBAM) larvae, Epiphyas postvittana (Walker) (Lepidoptera: Tortricidae) and LBAM larvae parasitised by Dolichogenidea tasmanica (Cameron) (Hymenoptera: Braconidae), an endoparasitoid. The two parasitoids co-exist in natural habitats, but D. tasmanica is numerically dominant in vineyards. Dolichogenidea tasmanica parasitises the early larval instars of LBAM, whilst G. jacintae parasitises the later instars. Both parasitise the 3rd instar of LBAM, suggesting that interspecific competition may occur. We tested the response of G. jacintae to hosts that had been parasitised either 1h or 168h previously by D. tasmanica. We also tested different sequences of host treatment exposure to G. jacintae. We found that G. jacintae attacked larger hosts more and laid more eggs on larger hosts, but that the probability of oviposition on the second host encountered was influenced by the parasitism status of both the current and the prior host. Clutch sizes laid on the first host were larger than clutches laid on the second host, but the number of eggs laid on the second host was influenced by host parasitism status. Finally, the proportion of attacks leading to oviposition was highest in unparasitised hosts and lowest in late-stage (168h) D. tasmanica parasitised hosts. Collectively, these results show that G. jacintae has some host discrimination abilities and adjust its responses according to prior experience, but does not avoid multiparasitism entirely.

The evolutionarily stable strategy, ESS, concept was first used in biology to understand sex ratio bias and, shortly afterwards, to explore the logic of contests over essential and indivisible resources. ESS models formed the basis of much subsequent research on animal behaviour and placed game-theoretic thinking firmly within the behavioural ecology approach. Among behavioural ecologists studying parasitoids, it was those asking questions about the evolution of sex ratios who first made extensive use of the game-theoretic approach. A later growth of interest in parasitoid host defence and fighting behaviour made use of these tractable study species to explore contests and their connections to further aspects of life-history evolution plus some pest control applications. Our aims are to (i) introduce the topic of contests, which are engaged in by a very wide array of animal taxa, and the importance, both historical and conceptual, of the game-theoretic approach to their study, and (ii) review recent studies of parasitoid contests, including those that have considered the context of social evolution and the performance of parasitoids as agents of biological control. We consider that game-theoretic models are eminently testable and applicable and will likely endure as valuable tools in studies of parasitoid biology.This article is part of the theme issue 'Half a century of evolutionary games: a synthesis of theory, application and future directions'.

Many animals lay their eggs in clusters. Eggs on the periphery of clusters can be at higher risk of mortality. We asked whether the most commonly occurring clutch sizes in pentatomid bugs could result from geometrical arrangements that maximize the proportion of eggs in the cluster’s interior. Although the most common clutch sizes do not correspond with geometric optimality, stink bugs do tend to lay clusters of eggs in shapes that protect increasing proportions of their offspring as clutch sizes increase. We also considered whether ovariole number, an aspect of reproductive anatomy that may be a fixed trait across many pentatomids, could explain observed distributions of clutch sizes. The most common clutch sizes across many species correspond with multiples of ovariole number. However, there are species with the same number of ovarioles that lay clutches of widely varying size, among which multiples of ovariole number are not over-represented. In pentatomid bugs, reproductive anatomy appears to be more important than egg mass geometry in determining clutch size uniformity. In addition, within this group of animals that has lost most of its variation in ovariole number, clutches with a broad range of shapes and sizes may still be laid.