Rubbing behavior and morphology of van der Vecht's gland inBelonogaster petiolata (Hymenoptera: Vespidae)

Females of the social wasp, Belonogaster petiolata,rub the secretion of van der Vecht's gland, located on their terminal gastral sternite, onto the nest pedicel. In bioassays, the secretion was repellent to two species of ants, while shortchain acids were effective releasers of rubbing behavior. Rubbing was associated with pedicel enlargement and departure from the nest in preemergence colonies. Its frequency was high where wasps were often exposed to ants and low where ants were rare or absent. Rubbing also decreased significantly from the pre-to the postemergence stage of the colony cycle. In both stages, subordinate foundresses rubbed more often than queens or workers. These observations support the hypothesis that rubbing behavior and the secretion of van der Vecht's gland function in chemical defense of the nest against ant predation. The general morphology of the gland in B. petiolataresembles that of the four other independent-founding polistine wasp genera.     

A latitudinal gradient in intensity of applying ant-repellent substance to the nest petiole in paper wasps (Hymenoptera: Vespidae)

Summary Observations on pre-emergence, single-foundress colonies of Japanese paper wasps (Polistes) revealed that there was a latitudinal gradient in intensity of application of an ant-repellent substance (secreted by the metasomal sternum VI glands) to the nest petiole. Thus the lower the latitude, the more frequently a foundress rubbed ant repellent onto the nest petiole. Estimation of potential ant predation on wasp brood using bait traps showed that there was a positive correlation between the frequency of rubbing and potential predation pressure from ants which are guided predominantly by substrate cues for foraging. There was also a latitudinal gradient in the degree of temporal association of rubbing behavior with foraging: the lower the latitude, the more closely foundress departure from the nest was associated with rubbing. Enlargement of the nest petiole by applying oral secretion potentially obliterated previous coats of ant repellent; however, this behavior was not always followed by rubbing behavior. The ant-repellent chemical barrier around the nest petiole may have evolved in tropical regions of the world as a defense against ant predation on wasp brood. I argue that as ant predation pressure diminishes towards the cooler regions, so does selection maintaining the behavioral sequence where foundress departure from the nest is preceded by rubbing behavior.     

A comparison of nest construction behavior in two species ofPolistes paper wasps (Insecta,Hymenoptera: Vespidae)

Polistes fuscatus variatus (a north temperate wasp) andP. instabilis (a tropical wasp) begin building their nests by applying pulp in a linear sequence of steps: surface preparation, petiole, flat sheet, first cell. After the initiation of first cell there are multiple locations for pulp addition (petiole, new cell, old cell), which become increasingly varied inP. fuscatus as the nest grows (secondary petioles, comb back, substrate, and pupal caps). AlthoughP. fuscatus also adds oral secretion to the petiole, comb back, and pupal caps,P. instabilis only applies oral secretion and no pulp to these locations and does not build secondary petioles or place pulp on the substrate. Both species show a similar series of behavioral acts leading from pulp foraging to application. In both species queens initiate more cells than do subordinates; nonetheless, subordinates account for a large percentage of initiated cells. During pre-emergence and early post-emergence the majority of pulp is used for cell lengthening. BothP. instabilis andP. fuscatus show a bimodal pattern of growth in cell number. The numbers of cells in a mature comb at the end of the nesting cycle are similar in both species (P.f.=274.4 andP.i.=282.6 cells).     

An alternative strategy for maintenance of eusociality after nest destruction: new nest construction in a primitively eusocial wasp

Although nests are central to colonial life in social insects, nests are sometimes damaged by predators or natural disasters. After nest destruction, individuals usually construct new nests. In this case, a sophisticated mechanism like the scent trail pheromone used in large insect colonies that recruit individuals to new nest sites would be important for the maintenance of eusociality. In independent-founding Polistes wasps, it is well known that queens enforce workers physiologically on the natal nests even if evidence of trail pheromone use has not been exhibited. We investigated the effect of the queen on an alternative strategy for the maintenance of eusociality by first females after nest destruction in the primitively eusocial wasp Polistes chinensis. We predicted that the first females in queen-absent colonies have various behavioral options after nest destruction. Even if the females construct new nests cooperatively with other individuals, the new nest construction should be conducted more smoothly in queen-present colonies because the queens regulate the behavior of wasps. We made wasps construct new nests by removing the entire brood from existing nests. The presence of the queen did not cause variation in the alternative strategy of the first females, as the first females (workers) usually constructed new nests cooperatively irrespective of the queen-presence. Thus, the workers in the queenpresent colonies affiliated to the new nest construction more smoothly and constructed new nests more efficiently than workers in the queen-absent colonies. Our results suggest that the presence of the queen is important for maintaining eusociality in primitively eusocial wasps after nest destruction. Received 8 February 2005; revised 5 October 2005; accepted 17 October 2005.     

Pulp partitioning and worker specialization in polistine wasps (Hymenoptera,Vespidae, Polistinae)

The character of pulp partitioning was studied in three Palaearctic polistine wasps (Polistes dominula and P. gallicus in the Black Sea Biosphere Reserve, and Polistes nimpha in the Lugansk Nature Reserve, Ukraine) and in five Neotropical species (P. lanio, P. versicolor, Mischocyttarus injucundus, M. alfkeni, Metapolybia cingulata, and Protopolybia exigua in Trinidad). In independent-founding Polistes and Mischocyttarus species, all cases of pulp partitioning were connected with aggression on the part of the foundresses. An experimental increase of nesting density of P. dominula led to changes in the relative abundance of workers in the polyethic task groups. Some workers practically stopped hunting and switched over to pulp delivery; some of these workers possessed well-developed ovaries and were able to lay eggs. The experimentally removed part of the nest envelope in the swarm-founding wasp Metapolybia cingulata was restored only in colonies that included young workers. The specific features of nest building activity in independent-founding and swarm-founding polistine wasps are discussed.     

Comparison of investment in nest construction by the foundresses of consubgenericPolistes wasps,P. (polistes) riparius andP. (P.) chinensis (hymenoptera, vespidae)

Some metric characters of nests built during the founding phase by foundresses were compared between two consubgenericPolistes wasps,P. (Polistes) riparius andP. (P.) chinensis, the former of which inhabit higher latitudes. Volumes and dry weights ofP. riparius nests were strikingly larger than those ofP. chinensis, even when standardized by the foundress weight (2.5 times for volume and 2 times for weight), showing that foundresses ofP. riparius invest much more in the nest construction than those ofP. chinensis. However, percent weights of oral secretion used for nests to total nest weights were smaller inP. riparius than inP. chinensis (52.1% vs. 60.4%). The differences in the investment by foundresses of the two species in the construction and maintenance of nests were discussed in relation to climatic and other environmental factors.     

Colony defence against ants inVespa

Summary On Ishigaki Island in southern Japan, despite the prevalence of ants in the study area, none of the failures of 54Vespa affinis (L.) colonies located could be directly attributed to attacks from ants. The long vestibule of theV. affinis embryo nest was not effective in preventing access to the nest by small species of ants.V. affinis andV. tropica (L.) females produce a substance which is repellent to ants. The substance is produced by the 6th and 7th abdominal sternal glands and is thought to be applied to the embryo nest petiole via the sternal brush. As the substance is produced by workers and queens during the entire life of the colony, it probably has a dual function.     

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.     

Nest recognition in neighboring colonies: a comparison of two European species of Polistes wasps (P. dominulus and P. nimphus, Hymenoptera: Vespidae)

The ability of two species of Polistes wasps to distinguish their own from nearby nests was tested, following the procedure used by Espelie et al. Our experiments demonstrated that, in the laboratory, females of Polistes dominulus and Polistes nimphus preferentially selected their own nests rather than nearby nests. We also evaluated the role of odor cues in nest recognition by washing nests in hexane to remove the apolar solvent-soluble components of nest odor. Although P. nimphus females continued to discriminate nests even after washing, P. dominulus individuals failed to discriminate between their own and a foreign neighboring nest. In both species, wasps were able to recognize their own nests when nest extracts were subsequently reapplied to the nest surface. These results indicate that P. dominulus wasps recognize their nests through perception of nest odor. The ability of P. nimphus wasps to distinguish their own nests even after presumed removal of the nest odor is discussed. Received: January 27, 2000 / Accepted: May 22, 2000     

Diel changes of temperature in the nests of two Polybia species, P. paulista and P. occidentalis (Hymenoptera, Vespidae) in the subtropical climate

Temperatures in two mature Polybia nests were measured to study the thermal conditions of nests. Temperatures in a Polybia paulista nest were measured when it had adult wasps (trial 1) and after the adult wasps were removed (trial 2), and temperatures in a P. occidentalis nest were measured when inhabited by adult wasps (trial 3). In each trial, C–C thermocouples were set at four points in the nest and at two points outside to discover the ambient and substratum temperatures. In trial 1, nest temperatures basically followed the ambient temperature, but during the day the nest temperatures were lower than the ambient temperature and this relationship was reversed during the night. The temperature fluctuation of the inner substratum points was smaller than that of the outer points. The trend of trial 2 was closely similar to that of trial 1, showing a virtual lack of thermal effects from the presence of adult wasps. In trial 3, the changing pattern in the P. occidentalis nest showed a trend similar to that in the P. paulista nest, but the inside temperatures rose quickly when the nest received direct sunlight in the morning. From these results, thermal characteristics in the Polybia nests are discussed in relation to the nest architecture and their geographical distribution.     

Colony Membership, Division of Labor, and Genetic Relatedness Among Females of Colonies of Eustenogaster fraterna (Hymenoptera, Vespidae, Stenogastrinae)

To compare the social structure of primitively social wasps with that of communal breeding vertebrates, we used a new technique based on micro videocameras applied to the nest envelope to study the organization of behavior in Malaysian colonies of the stenogastrine wasp Eustenogaster fraterna. The reproductive division of labor in this species appears to be different from that reported so far in other species of Stenogastrinae: it is at a very primitive stage because the helpers work less hard and take fewer risks than the egg-layers. Nevertheless, the very low-risk tasks performed by the helpers (nest guarding and supply of abdominal secretion to the young larvae) are important for the colonies. Behavioral characters and ovarian development of the helpers suggest that females are only temporary helpers and that they wait to start their own production of offspring in the hope of inheriting the nest. Females of the same colony can be highly related, but in some colonies we found low-related individuals. The social organization of these wasps resembles that of vertebrate groups with helpers at the den, i.e., in the small number of individuals, the division of labor with limited reproductive inhibition, and the prolonged external work of the reproductive individuals. However, the main drive to sociality in these insects appears to be different, being based mainly on problems connected with short adult life and long immature brood development.     

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.     

Effects of nest paper hydrocarbons on nest and nestmate recognition in colonies ofPolistes metricus say

The role of nest paper hydrocarbons in nest and nestmate recognition for the social waspPolistes metricus was examined. Newly emergedP. metricus workers maintained in the laboratory spent four days alone on a fragment of nest paper that was subjected to one of the following tretments: untreated, extracted with hexane to remove surface hydrocarbons, or extracted with extract reapplied. Test wasps were returned to their natal nest with nestmates and observed for 1 h. Time spent on nest by test wasp and its behaviors were recorded. Wasps exposed to untreated and reapplied nest fragments spent an average of 34.13 and 31.75 min on their nests, respectively, while wasps from extracted fragments averaged 17.19 min. Behavior of wasps exposed to extracted paper differed significantly from wasps exposed to paper with hydrocarbons. These results suggest that exposure to nest paper hydrocarbons is important for both nest and nestmate recognition.     

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.     

Rediscovery of the workerless inquiline antPogonomyrmex colei and additional notes on natural history (Hymenoptera: Formicidae)

Summary Pogonomyrmex colei is a workerless inquiline ant known only from nests ofP. rugosus, its closest relative. Ten of 776 (1.3%) host nests were parasitized at a site in central Arizona, while none of 1499 potential host colonies were parasitized at two other locales. Colonies ofP. colei are perennial, and host alate females in 9 of 10 colonies demonstrates that host queens survive parasitism. Three of 10 colonies died over 19 colony years of observation, while only 1 of 601 colonies became newly parasitized. Mating occurs in morning for up to 2–3 days following summer and fall rains and in afternoon during cool fall days. Mating is intranidal just outside the nest entrance, with males returning to the natal nest. MaleP. colei may be flightless because their wing area is reduced compared to host males. Females fly from the nest and locate potential host colonies by following trunk trails. Workers are the largest barrier to nest establishment, as they removed over 90% ofP. colei females placed in trunk trails or that entered host nests. Males and females ofP. colei andP. anergismus, the only other congeneric inquiline species, are diminutive compared to their hosts, with females 30% lighter than host workers. Fat content is lower and water content is higher inP. colei andP. anergismus females than in their hosts.     

Preferential phenotypic association linked with cooperation in paper wasps

Animals can influence their social environment by preferentially associating with certain conspecifics. Such preferential association has gained increasing theoretical attention, as it may influence social evolution and population dynamics. However, relatively little empirical work has examined the occurrence of preferential association and its effects on cooperative group formation. Here, we test the factors associated with cooperative group formation in Polistes dominulus nest‐founding queen wasps. P. dominulus are a good system to study preferential association, as foundresses can nest alone or in groups and group membership is flexible. We found that both social and environmental factors were associated with partner choice. First, facial patterns were associated with cooperation. Wasps with more similar facial patterns were more likely to cooperate than wasps with less similar facial patterns. This preferential phenotypic association fits the theoretical criteria for the evolution of tag‐based cooperation. Season was also associated with cooperation; wasps on early‐season nests were more likely to cooperate than wasps on late‐season nests. High levels of aggression by nest owners during initial interactions were also correlated with lower probabilities of subsequent cooperation, suggesting that nest owners have some control over group membership. Other factors including body weight, weight similarity and nest productivity were not linked with cooperation. Overall, multiple factors influence cooperation in paper wasps, including facial pattern similarity. The occurrence of preferential phenotypic association in paper wasps is quite interesting and may influence the evolution of cooperation and population divergence in this group.     

Pupal experience and nestmate recognition in <Emphasis Type="Italic">Polistes dominula</Emphasis> wasps

Social insects can discriminate between nestmates and aliens by comparing the chemical phenotype of an individual with the neural representation of their own colony odor (template). For social paper wasps of the genus Polistes, a general recognition model has been proposed and tested on few North American species: wasps learn colonial recognition cues from the nest paper during the first hours after emergence as adults. However, a recent study revealed that workers of Polistes dominula do not necessarily use the nest paper for early post-emergence cue-learning, suggesting that cues used for the formation of the referent template in this species could be learned at different life stages. Pre-natal learning is a widespread phenomenon in animals and it can shape various behaviors in adults. Here, we investigated whether pre-imaginal learning affects later nestmate recognition in P. dominula wasps. We reared worker pupae in artificial conditions to test whether the absence of nest material, or the exposure to nest material taken from a foreign conspecific colony, during pupal development would alter the nestmate recognition ability in adult life. Our results show that wasps maintain their correct recognition ability regardless of the treatment, suggesting that wasps do not form their referent template during the pupal stage from the nest paper. Alternative hypotheses for template formation timing and source of recognition cues are discussed. Moreover, we investigated whether young wasps already possess, on their own body, reliable chemical cues to form a recognition template by self-referent phenotype matching.     

Parasite presence acts as a proximate cue in the nest-site selection process of the solitary digger wasp,Ammophila dysmica (Hymenoptera: Sphecidae)

Nest-site selection by the solitary ground-nesting wasp Ammophila dysmicaMenke was studied during 1982–1986 in California's Sierra Nevada Mountains. Digging females detected and discriminated among members of a complex of insect intruders, including a number of predators and parasites. In response to some natural enemies, wasps sometimes permanently abandoned nests under construction. These selective nest abandonments reduced the mean number of cleptoparasitic chrysidid wasps, Argochrysis armillaBohart, attending the excavation of completed nests. The number of A. armillaattending a nest excavation correlated positively with the probability of nest parasitism by this species. Selective nest abandonment may reduce parasitism rates.     

Social behaviour and social structure of Neotropical paper waspsMischocyttarus angulatus Richards andM. basimacula (Cameron)

Social behaviour and social structure of 2 Neotropical polistine wasps,Mischocyttrus angulatus andM. basimacula, were investigated in the Canal Area, Republic of Panama. About 80% ofM. angulatus colonies and a half ofM. basimacula colonies were founted by multiple females having mature eggs in their ovaries. All of single-female colonies examined failed before the emergence of the first progeny. During the pre-emergence period, neither biting nor chasing was observed among females coexisting on the multifemale nests of both species. Although one of the females tended to stay on her nest for most of the time (‘queen-like female’), she was often replaced by a different individual on differrent days. In the post-emergence period, however, frequent aggression among females (including the foundresses and the first brood adults) was observed. The roles of pleometrosis and dominance behaviour in social lives of the 2 species in the wet tropics are discussed.     

Social parasitism of <Emphasis Type="Italic">Polistes dominulus</Emphasis> by <Emphasis Type="Italic">Polistes nimphus</Emphasis> (Hymenoptera,Vespidae)

Summary Interspecific facultative social parasitism is well known in ants and in bumble-bees, but it is rarer in wasps. This form of parasitism is traditionally considered to be an intermediate stage in the evolution of obligate interspecific parasitism, where the parasites are no longer able to nest alone. We report field and experimental observations of a newly discovered facultative parasitic relationship between two closely related free-living Polistes species: P. nimphus and P. dominulus. P. nimphus foundresses sometimes usurp the nests of the larger P. dominulus before worker emergence. The invading queen takes over the nest with abundant abdomen stroking on the nest surface and is accepted by workers if they emerge 6 or more days after usurpation. Morphometric comparisons show that the usurper species, though smaller than its victims, has morphological adaptations consisting of larger heads, mandibles and front femora relative to their body size that may give it an advantage during nest invasion. This strategy is likely to be taken only after the foundress loses her original nest because invading P. nimphus queens have lower reproductive success than they would have had on their own nest. Overall, we found that P. nimphus usurpers use strategies of invasion similar to those of two obligate parasites, suggesting that this may be an example of one of the pathways by which social parasitism evolved.Received 4 April 2003; revised 8 August 2003; accepted 14 September 2003.