The presence of statocysts and statoliths in social wasps (Hymenoptera, Vespinae)

Static sense organs composed of a hollow statocyst surrounded by sensory hairs and containing aggregate bodies (statoliths) have been detected in various species of Vespinae. On the frons in the groove traversing its center (the frontal groove) there is a deep pit and around it a membrane enclosing a cyst-like sac. In Vespa orientalis there are silicon (Si) and calcium (Ca)-containing aggregates inside the pit arranged in morula-like fashion, and in V. crabro, there are similar aggregates arranged in an ear-like shape. In general this sensillar organ resembles the statocyst located on the bases of the antennules in decapod crustaceans.     

Effects of prey quality on social wasps when given a choice of prey

The effect of prey quality on foraging behavior and colony demographics of the social wasp Polistes fuscatus was examined by providing a choice between non‐toxic prey (Manduca sexta caterpillars) and sublethally toxic prey (Junonia coenia caterpillars), and then comparing the performance of these colonies to others given only the non‐toxic prey. In the choice, one of two types of Manduca were used: those fed an artificial diet or those fed plantain (Plantago lanceolata), which contains iridoid glycosides (IGs) that Junonia coenia store but which Manduca does not. Despite the negative correlation between the number of Junonia prey used and number of adult offspring produced, when a surplus of non‐toxic prey was available, the wasps did not completely avoid the toxic prey. However, they were more discriminating when the choice was between Manduca fed an artificial diet and Junonia fed plantain vs. when both prey species had eaten the plantain. Because the wasps had a choice of prey types and had a surplus of prey on about one‐third of the days, the wasps were able to take enough non‐toxic prey to avoid some of the negative consequences of IGs. For example, the total number of wasp offspring per nest was not affected, but mean weight of female offspring per colony was less for colonies given both prey types eating plantain, compared to that for colonies fed only non‐toxic prey, or those given a choice of non‐toxic prey vs. toxic prey. In addition, compared to the control (only non‐toxic prey), the proportion of males produced was less in the treatment that provided a clear contrast between non‐toxic and toxic prey. Why these wasps did not avoid the toxic prey is discussed.     

Ovarian egg size and number in relation to female size in five species of parasitoid wasps

Within five species of parasitoid wasps of the families Pteromalidae ( Morodora armata Gahan, Muscidifurax zaraptor K. & L., Nasonia vitripennis (Walker)), Bethylidae ( Goniozus legneri Gordh), and Tiphiidae ( Myzinum quinquecinctum (Fabricius)), we found significant positive correlations between female body size and both the number and the size of the mature oocytes present in the ovaries. These data are discussed with reference to current clutch size and egg size models and biological information available on these species.     

Relationship between body size and flying-related structures in Neotropical social wasps (Polistinae,Vespidae, Hymenoptera)

Body size influences wing shape and associated muscles in flying animals which is a conspicuous phenomenon in insects, given their wide range in body size. Despite the significance of this, to date, no detailed study has been conducted across a group of species with similar biology allowing a look at specific relationship between body size and flying structures. Neotropical social vespids are a model group to study this problem as they are strong predators that rely heavily on flight while exhibiting a wide range in body size. In this paper we describe the variation in both wing shape, as wing planform, and mesosoma muscle size along the body size gradient of the Neotropical social wasps and discuss the potential factors affecting these changes. Analyses of 56 species were conducted using geometric morphometrics for the wings and lineal morphometrics for the body; independent contrast method regressions were used to correct for the phylogenetic effect. Smaller vespid species exhibit rounded wings, veins that are more concentrated in the proximal region, larger stigmata and the mesosoma is proportionally larger than in larger species. Meanwhile, larger species have more elongated wings, more distally extended venation, smaller stigmata and a proportionally smaller mesosoma. The differences in wing shape and other traits could be related to differences in flight demands caused by smaller and larger body sizes. Species around the extremes of body size distribution may invest more in flight muscle mass than species of intermediate sizes.     

Activity budgets, habitat use and body size in two coexisting species of sand wasps (Microbembex: Sphecidae, Hymenoptera)

ABSTRACT. 1. Two superficially similar species of Microbembex, M.monodonta (Say) and M.cubana Bohart (Hymenoptera, Sphecidae, Nyssoninae), occur syntopically on Staniel Cay, a small Bahamian island (15 km²).
2. Nesting (female) and territorial (male) aggregations of M.cubana were smaller and more numerous than those of M.monodonta in the study site and on the island as a whole.
3. Both species had regular patterns of daily activities that required them to use a variety of microhabitats in the study area.
4. Males of both species defended territories from c. 09.00 to 12.00 hours EST (in May) and the left to feed on nectar until they retired to sleeping burrows, typically from 13.00 to 15.00 hours. Male M.monodonta were active longer each day and intermixed feeding and territorial defence more than did male M.cubana.
5. Females of both species were active for longer each day, from c. 08.30 to 15.30 hours, and intermixed their respective activities – hunting for provisions, feeding, and nest digging and maintenance – during each day more than did males. Female M.monodonta were active longer each day, rising earlier and retiring later, than female M.cubana.
6. In M.monodonta , females were larger (length, X =11.00 mm) than males (10.5 mm). In M.cubana , males were larger (11.1 mm) than females (10.4 mm). Although mean differences were small, they were highly significant ( F =22.42; P <10⁻⁴) for the species-sex interaction.
7. Differences in activity budgets, habitat use, and sexual size dimorphism appear to be related. A combination of factors, particularly thermal constraints, possible competition, and different mating systems, could explain these patterns.     

Sampling methods for assessing social wasps species diversity in a eucalyptus plantation

Social wasps were collected in a eucalyptus (Eucalyptus urograndis, a genetically enhanced eucalyptus) plantation in Juiz de Fora, state of Minas Gerais, southwestern of Brazil, by using a variety of sampling methods, including active capture and baited traps set at two microhabitats. Six new records of social wasps for this region were obtained during the study: Brachygastra lecheguana Latreille, Polybia ignobilis Haliday, Polybia occidentalis Olivier, Polybia platycephala (Richards), Protonectarina sylveirae Saussure, and Protopolybia exigua Saussure (Hymenoptera: Vespidae). The active capture method sampled the greatest number of species. Baited traps installed in the canopy sampled agreater number of individuals of social wasps than those set on the trunks of eucalyptus trees. Fruit based baits captured a greater number of social wasp species than those baited with a protein derivative. Once no method was able to sample all species, we concluded that the efficiency of a survey can be maximized by using traps with a variety of different baits, in combination with active capture methods.     

Asymmetric larval competition between two species of solitary parasitoid wasps: the influence of superparasitism

Abstract.

• 1 We test the hypothesis that a solitary parasitoid wasp may gain in fitness if she lays more eggs in a host.
• 2 Using heterospecific superparasitism (=multiparasitism) between the solitary aphid parasitoids, Aphidius smithi Sharma & Subba Rao and Ephedrus californicus Baker, we show that (i) a superparasitizing female's chance that her offspring will survive competition is an increasing function of egg density, and (ii) survival among same-aged larvae is independent of the oviposition sequence.
• 3 These findings on asymmetric larval competition provide indirect evidence that supports two fundamental, but untested, assumptions underlying models of adaptive superparasitism between conspecific wasps.

     

Recognition and social dominance inPolistes wasps

It has been known for a long time that relationships among femalePolistes wasps are controlled by dominance through linear hierarchy. A classical model of the development of social hierarchies suggests that individual recognition intervenes to maintain the hierarchy established after the initial confrontation that takes place when two animals meet for the first time. This hypothesis was tested in the present study onPolistes gallicus (L.) foundresses. A tolerance index was calculated from the reactions of a dominant female when already known or unacquainted females were successively encountered. Results show that individualised social recognition is possible and that it takes more than 4 h of inter-individual contact for individual characteristics to be memorised.     

Optimal choice of species and size class for transplanting coral community

Transplantation of sessile organisms living in a planned destruction site to a safe site is an important means of restoration to mitigate biodiversity loss following anthropogenic developments. In particular, corals, which play fundamental roles in the coral reef ecosystem and contribute to biodiversity, are good candidates for transplantation. In this study, we investigate the optimal choice of species and size class to be used for coral transplantation. We first studied a case in which the objective function to evaluate the success of transplantation is the maximum total coverage. The optimal strategy is to choose the species and size class with higher net coverage gain per unit handling effort. It is often recommended to transplant only one or a few species and neglect others, even if the original community consists of many species. This may achieve high coverage in the restored coral community but cause loss of species diversity. To overcome this problem, we next study a case in which the objective of the transplantation operation is to maximize the “prosperity index”, defined as the product of total coverage and species diversity. In this case, the optimal strategy depends on the species property, population size, and the limitation of total cost allowed for transplantation, but it tends to recommend more species to be transplanted than what is recommended by the coverage maximization criterion. We conclude that maximization of the prosperity index is a better criterion for transplantation than simple coverage maximization.     

Effects of human presence on two social wasp species

Abstract.  1. The effects of human presence on the behavioural response and productivity of a native wasp species of North America ( Polistes fuscatus ) and an invasive wasp species ( Polistes dominulus ) were examined in a field experiment. Over a 3-month period, colonies of each species were exposed to human presence at either low (biweekly) or high (daily) levels. At 2-week intervals, wasp response to human presence was recorded for all colonies via an index, ranging from no response (0) to an attack (4).
2. The levels of human presence had no effect on wasp response or colony productivity but foundresses of both species increased their response level the closer a human was to the nest. In addition, foundresses of P. fuscatus became more aggressive over time, corresponding to after adult offspring emerged, whereas foundresses of P. dominulus did not change their response level after the emergence of offspring.
3. The adult offspring of P. dominulus responded to human presence at a level similar to that of the foundress, whereas adult offspring of P. fuscatus exhibited a lower response to human presence than that of the foundress. The more distinctive aposematic coloration of P. dominulus may play a role in the behavioural differences between species; it may be more effective in deterring predators, and with the result that leaving the nest to defend it is less often necessary. Accordingly, the less aggressive response to human presence by P. dominulus may contribute to its success as an introduced species in North America.     

Visual sensitivity and foraging in social wasps

Summary While there is a distinction between that intensity of illumination which permits social wasps to forage, and that to which a sessile worker can respond, nevertheless illumination is the most critical of the environmental factors which control the activity of wasps. Low temperatures, high winds, and heavy rain all reduce activity but unless exceptionally severe do not wholly stop it. At dawn, when the critical level of illumination is attained, workers leave the nest, but at dusk they will not leave should the same critical level be due in the course of the foraging flight, after which they could not return.The three species of wasp,Vespula vulgaris, V. rufa, andV. germanica have a common threshold of illumination, although the hornet,Vespa crabro can forage in moonlight at an altogether lower illumination. Honey-bees normally need a still higher illumination than do wasps.In all these species, the thresholds of illumination are related to the length of the compound eyes, so that species with large eyes need less light by which to forage. Moreover, there is a slight difference between the threshold at dawn when workers leave the nest, and that at dusk, when they must needs have sufficient light by which to return. This difference is almost constant for each species, when, as is customary, one measures it on a logarithmic scale.Lastly, the estimates, which these experiments provide, of the threshold illuminations depend stochastically on the number of workers foraging. A correction for this bias is given.

---

Sommaire Parmi les facteurs du milieu qui contrôlent l'activité des guêpes, celui de l'intensité de lumière est le plus important; toutefois on note une différence entre l'intensité de lumière qui permet aux guêpes sociales de fourrager, et celle qui produit une réponse des ouvrières sessiles.En général, les basses températures, les vents forts, et les grandes pluies réduisent leur activité, mais ces facteurs ne l'arrêtent pas complètement, à moins qu'ils ne soient très marqués.A l'aube, quand le niveau critique de lumière est atteint, les ouvrières quittent le guêpier, mais, le soir, si elles s'attendent à ce que la lumière vienne à s'abaisser au cours de leur sortie au-dessous du niveau critique, elles ne sortent pas.Les trois espèces de guêpe,Vespula vulgaris, V. rufa, etV. germanica, réagissent au même seuil de lumière, mais le frelon,Vespa crabro, est capable de fourrager au clair de lune par une lumière moins intense. Normalement, les abeilles exigent une lumière plus intense que les guêpes.Dans toutes ces espèces, le seuil de lumière se rapporte à la hauteur des yeux composés, par conséquent les espèces pourvues de grands yeux sont à même de fourrager par une lumière moins intense. De plus, il y a une légère différence entre le seuil de lumière à l'aube, quand les ouvrières quittent le guêpier, et celui du soir lorsqu'elles ont besoin d'une lumière suffisante pour rentrer. Cette différence, quand elle est mesurée à l'échelle logarithmique, comme il est d'usage, est presque constante pour chaque espèce.Enfin, les évaluations du seuil de lumière dans ces expériences dépendent stochastiquement du nombre d'ouvrières en train de fourrager. On a tenu compte de ce fait.

     

Survival and population size of a resident bird species are declining as temperature increases

1. A large number of migratory bird species appear to be declining as the result of climate change, but whether resident bird species have or will be adversely affected by climate change is less clear. We focus on the South Hills crossbill (Loxia curvirostra complex), which is endemic to about 70 km(2) of Rocky Mountain lodgepole pine (Pinus contorta latifolia) forest in southern Idaho, USA. 2. Our results indicate that the South Hills crossbill has declined by over 60% between 2003 and 2008, and that decreasing adult survival drives this population decline. 3. We evaluated the relative support for multiple hypotheses linking crossbill survival to climate, an ectoparasitic mite (scaly-leg mites Knemidokoptes jamaicensis), and the recent emergence of West Nile virus. Changes in adult apparent survival rate were closely associated with average spring and annual temperatures, and with high temperatures (≥32 °C) during summer, which have increased during the last decade. In contrast, there was little evidence that scaly-leg mites or West Nile virus contributed to recent declines in adult survival. 4. The most probable mechanism causing the decline in adult survival and population size is a decrease in the availability of their primary food resource, seeds in serotinous pine cones. Cone production has declined with increasing annual temperatures, and these cones appear to be prematurely opening owing to increasingly hot summer conditions releasing their seeds and reducing the carrying capacity for crossbills later in the year. 5. In light of regional climate change forecasts, which include an increase in both annual temperature and hot days (>32 °C), and the likely disappearance of lodgepole pine from southern Idaho by the end of this century, additional research is needed to determine how to maintain lodgepole pine forests and their supply of seeds to conserve one of the few bird species endemic to the continental United States.     

The influence of resident adults on larval settlement: experiments with four species of ascidians

Residents within any community can affect the larval settlement of both their own and other species. In marine sessile communities resident adults can affect larval settlement by preying on settling larvae, removing or adding space for the larvae to colonize, or stimulating or prohibiting larval settlement on available substratum nearby. To examine those processes by which residents affect settlement, we exposed experimental substrata with three densities of adults of a single species at a site in eastern Long Island Sound, USA for a 24-h period. Four species of common ascidians, Botryllus schlosseri (Pallas), Botrylloides diegensis Ritter and Forsyth, Diplosoma macdonaldi Herdman, and Molgula manhattensis (De Kay), were used in 11 separate experiments. Few individuals of any species settling attached to the surfaces of these species and this resulted in the main effect of these residents being the usurpation of space and the restricting of settlement to unoccupied areas. A model is also presented to explain the apparent aggregated settlement of several species in open areas adjacent to the resident ascidians. From this model we suggest that the aggregated settlement can result from limited larval mobility such that some larvae that contact and reject the resident species as settlement sites may subsequently contact open surfaces of the same substratum and increase settlement densities there over those observed on control substrata. Finally, settlement data for several species indicate that Molgula may influence settlement by preying on larvae.     

The influence of hunger on shoal size choice by three-spined sticklebacks, Gasterosteus aculeatus

Single sticklebacks ( Gasterosteus aculeatus ) were presented with a choice between (a) a shoal and an empty compartment, and (b) two different sized shoals of conspecifics. The choice of hungry test fish (food-deprived for 24 h and 72 h, respectively) was compared to that of fish which were fed to satiation once a day. It was hypothesized that due to the increased level of competition for food in large shoals, hungry fish would spend less time with the larger of two shoals than their well-fed conspecifics. The results showed that there was indeed a significant trend for test fish to spend a decreasing amount of time near the compartment with the larger number of fish with increasing duration of food deprivation.     

Egg predation within the nests of social wasps: a new genus and species of Phlaeothripidae,and evolutionary consequences of Thysanoptera invasive behaviour

The insects known as thrips are commonly thought of as flower‐living and pestiferous organisms, but we report here a novel interaction between a phlaeothripine thrips species, Mirothrips arbiter gen. et sp. nov. and three species of social paper wasps in Brazil. This thrips species breeds inside the wasp colonies, and larval and adult thrips feed on wasp eggs, which become severely damaged. Infested nests can contain up to 300 M. arbiter gen. et sp. nov. individuals. The closest relatives of M. arbiter are two presumably predaceous species: Mirothrips bicolor sp. nov. , which inhabits abandoned Cecidomyiidae galls, and Mirothrips analis comb. nov. , described from individuals collected in the silken bags of the caterpillars of Psychidae moths. The behaviour exhibited by M. arbiter represents one of the most evolutionarily advanced lifestyles known among Thysanoptera, and we predict that other polistine species serve as hosts for this thrips in Brazil. © 2013 The Linnean Society of London, Biological Journal of the Linnean Society, 2013, 109 , 332–341.     

Resource utilization and sex allocation in response to host size in two ectoparasitoid wasps on subcortical beetles

Patterns of host resource utilization and sex ratio manipulation in relation to host size were investigated for two solitary ectoparasitoid wasps,Atanycolus initiator andSpathius brevicaudis (Hymenoptera Braconidae). Both species parasitize subcortical beetles on the trunks of Japanese pine trees.A. initiator is on average 8 times larger in body weight and has an ovipositor that is 3.7 times longer than that ofS. brevicaudis. In both parasitoids, the size of emerging wasps was positively correlated with host size, but the host/wasp size regressions were linear for all three major host species inA. initiator, whereas inS. brevicaudis the regression was logarithmic for a relatively large host species. The sex ratios (proportion of males) of both parasitoids emerging from different host species decreased with increasing host size, but the overall sex ratio on each host species was male-biased inA. initiator, while female-biased inS. brevicaudis. How the proportion of host consumed changed in response to host size, differed between the two parasitoids for the same host species. In the field survey, the size and sex ratio of the emerging two parasitoids from a dead tree were closely related to host size. However, the spatial distribution of the two parasitoids depended on the bark thickness of the trunk. The data suggest that differences in the relative evaluation of host size and in ovipositor length may enable the coexistence of the two parasitoid wasps.     

Fitness in invasive social wasps: the role of variation in viral load,immune response and paternity in predicting nest size and reproductive output

Within any one habitat, the relative fitness of organisms in a population can vary substantially. Social insects like the common wasp are among the most successful invasive animals, but show enormous variation in nest size and other fitness‐related traits. Some of this variation may be caused by pathogens such as viruses that can have serious consequences in social insects, which range from reduced productivity to colony death. Both individual immune responses and colony‐level traits such as genetic diversity are likely to influence effects of pathogen infections on colony fitness. Here we investigate how infections with Kashmir Bee Virus (KBV), immune response and intracolony genetic diversity (due to queen polyandry) affect nest size in the invasive common wasp Vespula vulgaris. We show that KBV is highly prevalent in wasps and expression of antiviral immune genes is significantly increased with higher viral loads across individuals. Patriline membership within a nest did not influence KBV susceptibility or immune response. A permutational MANCOVA revealed that polyandry, viral load and expression of the immune gene Dicer were significant predictors of variation in nest size. High intracolony genetic diversity due to polyandry has previously been hypothesized to improve colony‐level resistance to parasites and pathogens. Consistent with this hypothesis, we observed genetically diverse colonies to be significantly larger and to produce more queens, although this effect was not driven by the pathogen we investigated. Invasive wasps clearly suffer from pathogens and expend resources, as indicated here by elevated immune gene expression, toward reducing pathogen‐impact on colony fitness.     

The influence of hunger,shoal size and predator presence on foraging in bluntnose minnows

This study examines the compromise between predator avoidance and foraging in bluntnose minnows, Pimephales notatus, in shoals of different sizes and at three levels of hunger: 5, 24 or 72 h of deprivation. Trials were carried out in the laboratory with a predator present or absent. Foraging was affected significantly by shoal size, predator presence and hunger. Foraging latency decreased as shoal size and hunger level increased, but latency increased in the presence of a predator. Foraging rate was less when there was a predator present. In the absence of a predator, foraging rate increased as hunger level increased. At the 5 h hunger level, foraging rate increased as shoal size increased, in the absence but not the presence of a predator. At this low level of hunger, innows in all shoal sizes fed at a low rate when the risk of predation was greater. At higher levels of hunger, fish in all shoal sizes fed at a high rate when no predator was present, so that foraging rate did not change across shoal size. When the predator was present at the higher hunger levels, only fish in larger, safer shoals fed at a rate greater than at the lowest hunger level.     

Invading species in the Eel River, California: successes, failures, and relationships with resident species

We examined invasions of non-native fishes into the Eel River, California. At least 16 species of fish have been introduced into the drainage which originally supported 12–14 fish species. Our study was prompted by the unauthorized introduction in 1979 of Sacramento squawfish, Ptychocheilus grandis, a large predatory cyprinid. From 1986 to 1990, we conducted growth and diet studies of squawfish, conducted intensive surveys of the distribution and habitat associations of both native and introduced species, and examined the nature of species-habitat and interspecies relationships. We found no evidence for increased growth or expanded feeding habits, compared to native populations, of Sacramento squawfish as they invaded the Eel River drainage. Ten of the introduced species were well established, with four species limited to a reservoir and six species established in streams. The success or failure of introductions of stream species appeared to be a function of the ability of a species to survive the fluctuating, highly seasonal, flow regime. The present mixture of native and exotic species has not formed stable fish assemblages but it seems likely that four habitat-associated assemblages will develop. The overall effect of the successful species introductions has been to assemble a group of species, with some exceptions, that are native to and occur together in many California streams. The assemblages now forming are similar to those found in other California streams. The assemblage characterized by squawfish and suckers is likely to be resistant to invasion, in the absence of human caused habitat modifications.