Queen succession in the primitively eusocial tropical waspRopalidia marginata (Lep.) (Hymenoptera: Vespidae)

Females of the primitively eusocial wasp Ropalidia marginata can be classified into three behavioral groups: Sitters, Fighters, and Foragers. It has been speculated that both Sitters and Fighters may be hopeful queens and that the Foragers may have little or no opportunities for direct reproduction. Here we show that in 9 of 12 queen-removal experiments where such a behavioral differentiation could be discerned, the individual that became a queen (the potential queen) was a Sitter in 6 cases, a Fighter in 2 cases, and a Forager in only 1 case. Although potential queens spent significantly more time absent from the nest and showed significantly higher rates of dominance behavior compared to the mean values for nonqueens in their colonies, they were intermediate with respect to all behaviors and age when compared to the range of values for nonqueens in their colonies. Potential queens were not necessarily the highest-ranking individuals among the nonqueens. The pattern of queen succession in this species appears to be quite different from the temperate pattern, where an old and active forager of high dominance rank is the potential queen. Although somewhat similar to the tropical pattern of a relatively younger female that has performed relatively little foraging being the potential queen, it is perhaps more accurate to describe the potential queens of R. marginata as unspecialized intermediates.     

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.     

The importance of location and visual cues during foraging in the German wasp (Vespula germanica F.) (Hymenoptera: Vespidae)

Abstract

The way in which foraging wasps use cues for prey location and choice appears to depend on both the context and on the type of prey. Vespula germanica is an opportunistic, generalist prey forager, and individual wasp foragers often return to hunt at sites of previous hunting success. In this paper, we studied which cues are used by this wasp when relocating a food source. Particularly we analysed the response to a displaced visual cue versus a foraging location at which either honey or cat food had been previously presented. We conclude that location is used over a displaced visual cue for directing wasp hovering, although the landing response is directed differently according to bait type. When wasps are exploiting cat food, location also elicits landing, but if they are exploiting honey, a displaced visual cue elicits landing more frequently than location.     

Variation in the quality of Vespula vulgaris (L.) queens (Hymenoptera: Vespidae) and its significance in wasp population dynamics

Abstract

Density‐related variation in queen quality has been proposed as a possible mechanism regulating population fluctuations in Vespula species. We investigated annual variation in the quality (size, weight, and fat content) of adult V. vulgaris queens representing four stages of their life cycle (spring, founding, developing, and emerged) taken from six sites in beech forest, South Island, New Zealand. For each queen the dry weight, head width, and thorax length was measured. For a subsample of queens, the fat content was determined by ether extraction. The size of queen cells was measured from a subsample of nests. Size, weight, and fat content of queens varied between wasp colonies and sites. The smallest juvenile queens were under‐represented in the reproductive population. There was no direct link between body size and food supply. Size and weight of developing queens increased as the number of cells in the nest increased. The size of the queen cells varied significantly among layers in a nest and among nests. The under‐representation of small queens in the reproductive population suggests that queen quality may affect survival and/or competitive ability by increasing winter fat storage, nest building activity, and/or success in usurpation disputes.     

Unmated queens in the primitively eusocial waspRopalidia marginata (Lep.) (Hymenoptera: Vespidae)

Summary In the primitively eusocial tropical waspRopalidia marginata, five out of eleven colonies studied had an unmated female as their queen. In two colonies this was the case despite the presence of another mated individual in the colony. We found no detectable differences between colonies with unmated queens and those with mated queens. We argue that in species such asR. marginata, where intracolony relatedness is expected to be low and where sociality is likely to be maintained because several individuals have opportunities for direct reproduction in the future, individual selection is likely to override the good of the colony and lead to such phenomena as that of unmated queens.     

How behavioral plasticity enables foraging under changing environmental conditions in the social wasp Vespula germanica(Hymenoptera:Vespidae)

The foraging strategy at abundant resources of the social wasp Vespula germanica includes scanning in the direction of the nest while memorizing resource-specific landmarks and contextual cues.In the present study,we sought to explore wasps'behavioral plasticity on foraging trips to resources whose location and composition changed after a single visit.We evaluated how contextual modifications of food displacement and replacements 60 cm apart from the original site,affect re-orientation for re-finding previously memorized food resources.The results showed that wasps detected and collected the resource faster when more changes were introduced on the following visit.If returning foragers discovered several modifications on both the location and the kind of resource,they collected food more rapidly from the displaced dish,than if only a single parameter in the environment had been changed.These findings illustrate the grade of behavioral plasticity in V.germanica while foraging on abundant resources,which may contribute to the understanding of the prodigious invasive success of this species in anthropized environments.     

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.     

Foraging and spatial dispersion in protein-scavenging workers ofVespula germanica andV. maculifrons (Hymenoptera: Vespidae)

A series of experiments on the discovery of meat bait by scavenging workers ofV. germanica andV. maculifrons showed that workers oriented to meats by visual cues and olfactory cues. Scavening workers ofV. germanica andV. maculifrons responded positively to the sight of conspecifics at meat baits; i.e., meat with (confined) wasps received more visits than meat without wasps. This attraction to conspecific workers on meat baits provides evidence of local enhancement, in that the presence of conspecifics at meat bait directs other wasps to a particular spatial locality. Local enhancement by yellowjackets foraging for meat may contribute to the clumped distribution of worker populations noted in studies of workers captured in meat-baited traps. We hypothesize that local enhancement of foraging is a ubiquitous behavior in species of theV. vulgaris species group and may be one attribute explaining their ecological success.     

Nonrandom visitation of brood cells by worker honey bees (Hymenoptera: Apidae)

The visitation pattern by worker honey bees to cells in the brood nest was monitored on an artificially created brood pattern consisting of about one-fourth brood cells evenly distributed among empty cells. The majority (63 %) of the observed workers selectively entered larval cells. In contrast, some workers avoided egg cells when presented a choice of egg vs empty cells. The results suggest that larvae produce a general signal indicating their presence to worker bees. Eggs also seem to produce a signal, which is perceived to be different from the one from larvae.     

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.     

Usurpations and late associations in the solitary founding social wasp,Polistes biglumis bimaculatus (Hymenoptera: Vespidae)

One hundred twenty-five colonies of a population of the montane, haplometrotic, paper waspPolistes biglumis bimaculatus were marked for identification and then periodically surveyed during an entire summer period. This made it possible to record intraspecific nest usurpations (both single and multiple) and to observe associations between two females, defined here as late associations. Both usurpation and late association occurred primarily in the latter half of the preemergence period. Some evidence suggests that a foundress usurps a conspecific nest as a consequence of her own nest failure. After nest failure, usurpation and late association are the only available options for achieving reproductive success because, in the mountain habitat, the short summer does not allow for successful renesting. Late associations generally occurred earlier than usurpation. However, our evidence suggests that nest usurpation and late association may be the same phenomenon.     

Structure of ovarioles in adult queens and workers of the common wasp, Vespula germanica (Hymenoptera: Vespidae)

The ovaries of the common wasp, Vespula germanica are polytrophic-meroistic and consist of 2-3 (workers) or 7 (queens) ovarioles. The ovarioles are differentiated into three regions: a terminal filament, a germarium, and a vitellarium. The germaria of both castes consist of two zones: an anterior zone of germ-cell cluster formation and a posterior one of germ-cell cluster differentiation. The vitellaria comprise 4-6 (workers) or 7-10 (queens) ovarian follicles (egg chambers). Each chamber consists of an oocyte and about 60 isodiametric nurse cells (trophocytes). The egg chambers have been arbitrarily classified into four developmental categories: early and late previtellogenic, vitellogenic, and choriogenic. The process of oogenesis in workers proceeds only up to the onset of the late previtellogenesis. Neither vitellogenic nor choriogenic egg chambers were observed in this caste. During early and late previtellogenesis the envelope of the oocyte nucleus proliferates and becomes highly folded. This process leads to the formation of characteristic organelles, termed accessory nuclei (AN). Although AN arise in the oocytes of both queens and workers, their number in the latter caste is always considerably lower. At the onset of the late previtellogenesis AN start to migrate towards the periphery of the oocyte where they reside till the end of oogenesis. The physiological state of the worker ovaries is discussed in the light of the presented results.     

A distinct caste difference inPolybioides tabidus (Fabricius) (Hymenoptera: Vespidae)

Summary Queens ofPolybioides tabidus differ from workers of the same species in the presence of very much longer bristles on the eyes and head and in the size of some morphological characters. The presence/absence of eye bristles in queens/workers of P. tabidus is the first qualitative morphological caste difference reported in the Polistinae.     

Characteristics of usurped colonies in the subtropical paper wasp,Ropalidia fasciata (Hymenoptera: Vespidae)

Summary Nest usurpation in the subtropical paper waspRopalidia fasciata was studied in Okinawa, southern Japan. Eight of 14 usurpations occurred around the first worker emergence (within 3 days before and 3 days after the emergence). A discriminant analysis showed that the usurpers preferred colonies that had fewer adult females and fewer cells but abundant pupae, compared with non-usurped colonies in the study area on same dates. This suggests that usurpers can assess the development of other colonies and then select a nest that is easy to usurp (fewer females) but has valuable resources (abundant pupae).     

Variation in colour markings of German wasps Vespula germanica (F.) and common wasps Vespula vulgaris (L.) (Hymenoptera: Vespidae) in New Zealand

Abstract

German wasps (Vespula germanica F.) and common wasps (V. vulgaris L.) both show variations in colour markings in New Zealand. Overlap in the ranges of markings of the head and thorax is limited enough for ready distinction of queens and workers of the two species. Abdominal markings overlap considerably between the species. Colour markings of males were too similar to identify the species, which were completely separated by the shape of their genitalia. The frequency of occurrence of “intermediate” markings in V. germanica populations did not increase in areas where the two species overlap. This suggests there is little or no genetic exchange between the two species.     

Occurrence of the common wasp,Vespula vulgaris (L.) (Hymenoptera: Vespidae) in New Zealand

Abstract

After occurring sporadically in New Zealand since 1921, the common wasp, Vespula vulgaris (L.), was found in March and April 1983 to be established in Dunedin, where 6 nests were discovered. Subsequent examination of museum specimens showed that queens had been collected in Wellington in 1978, and nests by January 1982. Christchurch was invaded in early 1984, several workers were collected near Auckland in March and April 1984, and workers were reported at Nelson in March and May 1984. The Dunedin nests were up to 6 times the size of nests recorded from the Northern Hemisphere, and produced up to 23 times as many new queens. Workers, nest size, and nest productivity were sufficiently different from those reported in western North America to suggest that the New Zealand population originated elsewhere. Colour patterning of the head and pronotum readily separate New Zealand V. vulgaris from New Zealand V. germanica. The nest carton of V. vulgaris is brown; that of V. germanica is grey. Conditions in New Zealand appear to be favourable for V. vulgaris; it can be expected to spread and it may at times reach the high population levels experienced in Europe and the western United States.     

Information analysis by the paper wasp,Polistes fuscatus,during nest construction (Hymenoptera,Vespidae)

Summary The building decision process of the paper wasp,Polistes fuscatus, was studied by 1) analyzing the search pattern of the wasps prior to the addition of pulp to different areas of the nest, 2) comparing the pulp addition needs of the cell chosen for lengthening to those of other cells in the nest, and 3) presenting the wasps with eight types of dichotomous building choices, which provided information about the relative influence of different building cues. Wasps conduct a hierarchical search prior to pulp addition, which means that they search the comb face and petiole disproportionately more often and more thoroughly than the comb back and sides. Once a particular nest area triggers closer scrutiny, comparisons are made with adjoining areas. The most needy location is then chosen based on nest cues. When lengthening a cell, the development of the brood and relative cell length have a strong influence on which cell is chosen at all times, while distance of the brood from the cell mouth becomes important during the later stages of brood development. The results indicate that there is no simple hierarchical weighting of cues. The decision process involves comparisons among multiple cues, which for the most part have an additive influence when variation in relative cue strength is considered.     

Nest surface hydrocarbons facilitate nestmate recognition for the social wasp,Polistes metricus Say (Hymenoptera: Vespidae)

Nestmate recognition was observed inPolistes metricus Say workers only if the workers were exposed to their nest surface hydrocarbons after eclosion. If the newly emerged workers were never exposed to the nest hydrocarbons as adults, they showed no discrimination between nestmates and nonnestmates. Furthermore, the newly emerged workers were accepted more readily by their experienced nestmates than by experienced nonnestmates only if the newly emerged wasps had been exposed to the nest surface hydrocarbons. This reciprocal recognition implies that the nest recognition cues are nest surface hydrocarbons that are learned and that may be acquired byP. metricus workers as adults on the natal nest.