Age polyethism and defense in a tropical social wasp (Hymenoptera: Vespidae)

Although tapping the nest in simulated vertebrate attack caused all but 1-day-old workers of Polybia occidentalis to rush from inside and cover the envelope, defense itself—attack of a target—was shown to be carried out only by workers older than about 10 days. While foraging was also performed by older workers, the frequency-age distribution of defensive behavior was skewed to a significantly younger age than was that of foraging. The plot of mean individual probability of defending as a function of age was logistic, leveling off at 0.11 by the age of about 13 days. The distribution of the probability of defending among workers 13 days of age was random, indicating that there is no specialized defender class among older workers. Workers that defended were recruited from among both nest workers and foragers. Although foragers were more likely to defend than were nonforagers, nonforagers contributed more individuals to the pool of defenders because they were more numerous.     

Site selection by a social wasp in a nesting association (Hymenoptera: Vespidae)

The tropical social waspMischocyttarus immarginatus is a nesting associate ofPolybia occidentalis in northwestern Costa Rica. We show that an activeP. occidentalis colony is a necessary component of aM. immarginatus nesting site in this part of the latter’s range.M. immarginatus foundresses actively seekP. occidentalis colonies to initiate nests at a modal distance of 8 cm from them. There is an 18-mm lower limit to how closeM. immarginatus can nest in relation toP. occidentalis. At distances of less than this,P. occidentalis workers can reach theM. immarginatus nest while standing on their own nest and robM. immarginatus of its brood when the adults are absent.     

Size and composition of swarming colonies in Provespa anomala (Hymenoptera, Vespidae), a nocturnal social wasp

Summary: Ninety-eight nests of various growing stages of Provespa anomala were found in the lowlands of Sumatra, Indonesia, from August to January. Its colony cycle is considered to be annual, with nests built throughout the year. There were two types of early nests before the emergence of workers, one with a worker number of less than 63 and the other of more than 231. The former were new nests, each containing a new queen and were built by reproductive swarming, whereas each of the latter was possibly re-built by an old queen and an absconding swarm. Ten swarming colonies were attracted by an oil-lamp light; these consisted of a copulated queen with immature oocytes in the ovary and 55 workers on average. No males, or workers stylopized by Xenos provesparum were observed either in colonies before worker emergence or in swarms coming flying into the light. Differences between swarming in Provespa, polygyny and nest relocation in Vespa, and those in swarm-founding Polistinae are discussed.     

Metapolybia araujoi,a new species of swarming social wasp from the Brazilian Amazon rainforest (Vespidae: Polistinae)

A new species of Metapolybia, collected in Pará State, Brazil, by Adolph Ducke, in 1902, is described and comparative remarks are given.     

Three new host species of the social wasp parasite, Polistes atrimandibularis (Hymenoptera, Vespidae)

Summary. We report that the social parasite Polistes atrimandibularis (Zimmermann) can exploit at least three more host species than previously described. One of these, P. associus, has never been reported as host of a social parasite. Our data show no constraints in host choice, indicating P. atrimandibularis is a generalist social parasite.     

Bionomic notes on Pachysomoides sp. (Hymenoptera: Ichneumonidae), a parasitoid of the Neotropical social wasp Polistes satan Bequaert (Hymenoptera: Vespidae)

Although most polistine wasp species are found in the Neotropical region, mainly in Brazil, only a very limited number of South American parasitoids or parasites are known to exist. We assessed the frequency of a hymenopterous parasitoid, Pachysomoides sp. (Ichneumonidae, Cryptinae), in the nests of the Brazilian independent‐founding wasp Polistes satan and compared the rates of the parasitization of P. satan by Pachysomoides sp. between the dry (winter) and wet (summer) seasons. Pachysomoides sp. larvae were seen to feed on P. satan pupa and were found in both the upper and lower parts of the host pupal cell (ca. 10 individuals in each host pupal cell). Approximately one‐third of the pupal cells in the P. satan colonies were parasitized in the dry season, whereas there were no parasitized pupal cells in the wet season. Consequently, the rates of parasitization by Pachysomoides sp. were significantly greater during the dry season than during the wet season due to unknown reasons.     

Proteomic analysis of the venom of the social wasp Apoica pallens (Hymenoptera: Vespidae)

Wasps are a diverse group of insects that possess a sting apparatus associated with a venom gland, which is used for predation and colony defense. The biochemistry of Hymenoptera venom has been evaluated in relation to allergy and immunology, and proteomics has been shown to be a powerful tool for the identification of compounds with pharmacological potential. Data on wasps venom the of genus Apoica are scarce, so the objective of the present work was to identify the venom proteins of the eusocial wasp Apoica pallens, as a first step towards further investigation of applied uses of the venom and its protein constituents. The venom proteins were separated by two-dimensional gel electrophoresis, followed by MALDI-TOF/TOF mass spectrometry. A total of 259 spots were detected, with molecular weights from 4.9 to 141 kDa. Thirty of these proteins were identified and classified into eight functional categories: allergen, enzyme, metabolism, structural, environmental response, proteoglycan, active in DNA and RNA, and unknown function. Due to the few available proteomic data for wasp venom, many proteins could not be identified, which makes studies with proteomic analysis of Hymenoptera venom even more important.     

Altitudinal distribution and body resource allocation in a high mountain social wasp (Hymenoptera: Vespidae)

Jame's rule proposes a direct relationship between body size and altitude. There are several studies about this rule; however, few studies analyze proportional changes in body parts along gradients. The morphological variation of Agelaia pallipes (Olivier) in five sites along an altitudinal gradient (2600-3380 m) in the Santuario de Iguaque, Colombia, were studied in order to test whether or not the species follows Jame's rule, and whether body parts follow a homogeneous variation. Body variation analysis was conducted through multivariate analysis of variance (MANOVA) and the relationship between altitude and each morphometric measurement was studied through regression analyses. The MANOVA indicated significant differences among sites. An increase in altitude leads to a reduction in body size, especially in hind femur length and head width. However, measurements linked to flight such as mesosoma height, mesoscutum width, and fore wing size showed a reverse tendency. Possibly all described changes are consequence of both reduction on food availability and lower atmospheric pressure. The low temperature of high areas may strongly limit foraging and thus food availability. Lower atmospheric pressure reduces flight potential and may result in an increase in size of both wings and flight muscles. This paper underscores the need to study in detail the changes in body proportions in species with wide distribution ranges in latitude and altitude.     

Aspects of worker reproduction in four social wasp species (Insecta: Hymenoptera: Vespidae)

The question of male production by workers in social wasp colonies (Vespinae) has long concerned researchers. Its occurrence would suggest that queen control of colony reproduction is not absolute and that the evolution and maintenance of eusociality in vespines may have been promoted through direct reproductive ability of the worker caste. Dissections of over 3,300 workers from 34 Paravespula and Vespula colonies failed to reveal a significant contribution to male production by workers in most colonies. In those colonies which did contain ovary-developed workers, the wasps tended to be larger than their nestmates in two of the species. On the other hand, ovary-developed workers could not be characterized as specializing in intra- or extranidal tasks in any species. The onset of worker ovarian development was associated with increased size of nests and occurred predominantly in late-season colonies. The near-complete sterility of workers through most of the season suggests that models invoking mutualism and characterizing workers as 'hopeful reproductives' cannot explain the maintenance of eusociality in vespine wasps.     

Venom spraying inParachartergus colobopterus: A novel defensive behavior in a social wasp (Hymenoptera: Vespidae)

Colonies ofParachartergus colobopterus do not defend against vertebrates by attacking and stinging. Instead, defending workers bend the gaster forward and spray a fine mist of venom in the direction of nearby moving objects. Although venom spraying has been reported forP. fraternus, a species that does sting, we found that this occurred only during sting attempts. We conclude that defensive behavior inP. colobopterus is unique among wasps in that (1) venom is sprayed at intruders by workers standing on the nest and (2) the spray is an atomized mist rather than a stream. We suggest that nest crypticity restricts vertebrate predators on this wasp to small, insect gleaning birds, against which a spray of venom in the eyes, mouth, and nasal passages is more effective than is a stinging defense.     

Ultrastructural features of the hypopharyngeal glands in the social wasp Polistes versicolor (Hymenoptera: Vespidae)

The wasps of the genus Polistes have been considered the key to understanding the evolution of social behavior in Hymenoptera. Several studies have shown that the development of organized insect societies was accompanied by the evolution of structures like exocrine glands, which became specialized to perform specific functions. This article investigates the ultrastructural and cytochemical features of the hypopharyngeal glands of Polistes versicolor. These glands have been studied in depth in social bees, where they occur only in nurses and produce the royal jelly. Our results revealed that these glands basically did not vary among individuals or between sexes. They are constituted by spherical cells, each with a large nucleus and well‐developed rough endoplasmic reticulum. Secretion vesicles are abundant, but lipid droplets were not observed, indicating that these glands may not have a role in pheromone synthesis. Acid phosphatase was detected in lysosomes, and also free in the cytosol, but did not seem to be related with cell death. Thus, our results suggest that the hypopharyngeal glands of P. versicolor may not have a specialized social role, but could produce digestive enzymes.     

The chemical strategies used by Polistes nimphus social wasp usurpers (Hymenoptera Vespidae)

Polistes foundresses can behave as facultative social parasites when, instead of founding their own nest, they usurp colonies of the same or a different species and temporary use the host workforce to raise their own brood. Conspecific usurpation appears to be common among Polistes wasps, but nothing is known about the mechanisms that these facultative social parasites use to have themselves accepted within usurped colonies. Using behavioural tests, we studied the chemical strategies employed by females of Polistes nimphus when they behave as facultative social parasites in colonies of the same or of a different species. We hypothesized that usurpers would mark host nests with their own odours and/or acquire host nest odours in order to camouflage their real identity from host workers. Our results indicated that P. nimphus usurpers used different chemical strategies depending on host nest species: they acquired conspecific host odours but marked heterospecific host combs with their own odours.  © 2007 The Linnean Society of London, Biological Journal of the Linnean Society , 2007, 91 , 505–512.     

Behaviour of the Indian social wasp Ropalidia cyathiformis on a nest of separate combs (Hymenoptera: Vespidae)

Observations were made on a nest of Ropalidia cyathiformis consisting of three combs. The number of eggs, larvae, pupae and adults were monitored at about 3-day intervals for a 2-month period. The behaviour of the adults was observed with special reference to the proportion of time spent on each of the three combs, the proportion of time spent away from the nest site and the frequencies of dominance interactions and egg laying. The adults moved freely between the three combs suggesting that all of them and all the three combs belonged to one nest. However, most of the adults preferred combs 2 and 3 over comb 1. Of the 10 animals chosen for a detailed analysis of behaviour, seven spent varying periods of time away from the nest site and oRen brought back food or building material. Five of the 10 animals laid at least one egg each but two adults monopolized most of the egg-laying. The animals showed a variety of dominance interactions on the basis of which they have been arranged in a dominance hierarchy. The dominant individuals laid most of the eggs and spent little or no time foraging, while the subordinate individuals spent more time foraging and laid few eggs or none. It is argued that R. cyathiformis is different from R. marginata , the only other Indian social wasp whose behaviour has been studied, in being at a more primitive stage of social organization.     

Genetic relatedness and population structure in the social wasp,Mischocyttarus mexicanus (Hymenoptera: Vespidae)

Summary In primitively eusocial wasps workers often retain the ability to become queens, so their continued performance in the worker role is partly dependent on elevated genetic relatedness between workers and the brood they rear. In colonies of the social wasp,Mischocyttarus mexicanus, workers were related to female pupae by 0.29±0.12, a value that is significantly below the full sister value of 0.75, but not significantly below 0.50, worker relatedness to daughters. Though individuals often build new nests within meters of their natal nest, there was no genetic population structure discernable among four nest clusters, or inbreeding of any kind.     

Observations onApoica pallens,a nocturnal neotropical social wasp (Hymenoptera: Vespidae,Polistinae, Epiponini)

Summary Colonies and nests ofApoica pallens in the llanos region of Venezuela range from small foundress nests to large mature colonies. Nests are sited on small diameter, near-horizontal branches in a variety of shrub and tree species. During the day, adult wasps cluster on the face of the nest in an array that seems to be determined by orientation to gravity; defense of the colony against parasitoids and ants by the resting wasps may be more a passive than an active behavior. Wasps fan their wings to cool the colony during the day, but no foraging for water accompanies the fanning behavior. Nightly foraging activity begins with the explosive departure from the nest of hundreds of wasps, most of which rapidly return. Moderate foraging levels early at night give way to very low foraging levels in pre-dawn hours. The period of moderate foraging may be extended for longer hours during increased moonlight. Foraging wasps collect arthropod provisions for larvae. Larvae produce a trophallactic saliva; adults engage in inter-adult trophallaxis; brood are cannibalized. During cluster formation prior to swarm emigration, adult wasps do not appear to scent-mark substrates such as leaves. Instead,A. pallens exhibits a calling behavior, unique among polistine wasps studied to date, in which the gaster is held rigidly away from the thorax and metasomal sternal glands are exposed. Swarms can emigrate during the day.A. pallens may incorporate absconding and colony relocation as features of its colony cycle in the highly seasonal llanos.     

First records of Synoeca septentrionalis Richards, 1978 (Hymenoptera, Vespidae, Epiponini) in the Brazilian Atlantic Rain Forest

Nests of Synoeca septentrionalis were collected in two Brazilian Atlantic Rain Forest localities (Itabuna and Santa Terezinha, in the state of Bahia and Alfredo Chaves in the state of Espírito Santo). Synoeca septentrionalis was previously recorded only from Central America and northwestern South America. This findingextends its geographical distribution to Northeast and Southeast regions of Brazil, and represents the first record for Synoeca septentrionalis in the Brazilian Atlantic Rain forest, raising to three the number of Synoeca species known from Bahia State.     

Chemical analysis of the swarming trail pheromone of the social wasp Polybia sericea (Hymenoptera: Vespidae)

The behaviour of those polistine wasps which found their nests by swarming, suggests that these species use trail pheromones for leading the swarm to the location chosen for the new nest. Apart from a recent report regarding the ropalidine Polybioides tabidus, where the pheromone is thought to originate from the Dufour gland, nothing is known about the chemistry of such pheromones. Polybia sericea is the only species for which the source of the trail pheromone, the Richards' gland, is known with certainty. The chemistry of the Richards' gland secretion of this species has been investigated in the present work and shown to be a complex mixture where the major compounds are alkyl and aromatic aldehydes, fatty acids, 3-phenylpropanoic acid, ketones, a macrolactone, a pyranone compound and nerolidol.