Male Reproductive Behavior of the Social Wasp Polistes fascatus (Hymenoptera: Vespidae)

Populations of male Polistes fuscatus simultaneously exhibit two different mate-locating tactics. Some males defend territories in female nesting and hibernation sites. These males frequently do not occupy the same territory each day, and they drag their gasters over perches, which may function to apply a secretion to the perch. Another segment of the population patrols large overlapping areas in female foraging sites. In contrast to territorial males, patrolling males do not rub their gasters on perches, and males seen on more than one day are tenacious to one area. Males in both sites are aggressive to other males and attempt to copulate with females. A laboratory study indicates that large males have an advantage in male-male competition. The mean size of patrollers is smaller than that of territorial males, indicating that patrollers are competitively inferior males. Yet there is considerable size overlap of males between the two sites, suggesting that there is also overlap in the range of probability of mating success between the two sites.     

The Function of Male Dominance in the Eusocial Wasp, Mischocyttarus mastigophorus (Hymenoptera: Vespidae)

Males of a Neotropical eusocial wasp, Mischocyttarus mastigophorus , are dominant over their female nest mates. Mischocyttarus mastigophorus males behave aggressively toward females, while females rarely bite or chase males. Aggressive interactions between the sexes are behaviorally indistinguishable from dominance interactions among females. Males are long-lived as adults, and can reside on nests for periods of at least one month. Furthermore, males comprise a large proportion of post-emergence colony populations throughout much of the colony cycle. Males on the nest perform maintenance tasks at low rates, but contribute little other labor to their colonies. Males do not forage, but consume a disproportionate amount of the food (nectar and insect prey) collected by workers. Males in some colonies direct disproportionate amounts of aggression toward their queens, which may further contribute to males' food procurement. These data suggest that adult males represent a considerable energetic and labor cost to their colonies. I hypothesize that the dominance structure of M. mastigophorus directs food resources to adult males, with the function of increasing their longevity. Increased male longevity may be selectively advantageous in tropical species such as M. mastigophorus that found new colonies throughout much or all of the year. When females initiate new nests over much of the year, individual males' mating opportunities may be temporally distributed, favoring longer adult lifespans. Male dominance is predicted to occur in other populations of independent-founding Neotropical Polistinae with asynchronous colony foundation.     

Application of Microsatellite Primers Developed for Polistes in the Independent-Founding Wasp Polists satan Bequaert (Hymenoptera: Vespidae)

Microsatellite primers developed for a given species are sometimes useful for another in the same genus and in other genera within the same family, making possible to search for pre-existing suitable primers in the databanks such as GenBank. We examined whether existing primers developed for Polistes could be used for Polistes satan Bequaert. We tested 50 microsatellite primers from three Polistes species and found that six microsatellite loci show polymorphism in size in P. satan. These six loci were highly polymorphic, having four to 15 alleles in P. satan with an expected heterozygosity of 0.525?C0.832. These loci can be used to study parameters concerning genetic relatedness such as social interactions in colonies and genetic conflicts of interest among nestmate individuals.     

Evolution of Swarm Communication in Eusocial Wasps (Hymenoptera: Vespidae)

Eusocial paper wasps, yellowjackets, and hornets (Vespidae) exhibit two modes of colony foundation, primitively eusocial independent founders and advanced eusocial swarm founders. Unlike independent founders, swarmfounding wasps require a means of social communication to coordinate the movement of colony members between nest sites. We employed a phylogeny of paper wasps, yellowjackets, and hornets to test for patterns of correlated evolution between the mode of colony foundation and the presence of sternal exocrine glands. We also reviewed data on worker actions during swarming to determine whether swarm communication behavior was dependent upon gland possession and whether communicative behavior was shared among swarm-founding species. We did not find evidence for an association of sternal glands with swarm founding. Although sternal gland presence differed among swarm-founding species, worker behavior during swarming showed little variation. Workers of nearly all swarm-founding species rub their gasters on objects along swarm routes, independently of the occurrence of sternal glands. Widespread gastral rubbing indicates the use of swarm emigration trail pheromones from a diversity of glandular sources. Transitions from independent to swarm founding have been achieved via diverse pheromonal mechanisms in the Vespidae, while worker communicative behavior is either highly conserved or convergent.     

Grooming Patterns in the Primitively Eusocial Wasp Polistes dominulus

Grooming is a commonly observed behavior in many animals. One function of grooming is to clean the body of debris and parasites. An additional function may be to homogenize chemical cues present on the body. This latter purpose is especially likely in species in which contact‐based chemical communication occurs, such as in eusocial insects. In this study we address the context, sequence, frequency and duration of 683 acts of self‐grooming performed by the paper wasp, Polistes dominulus. In general, individuals groomed heads after cell inspections, and abdomens after sitting, suggesting that grooming serves to remove debris from the body. Although no differences were observed in the total amount of time spent grooming, foundresses groomed significantly more often than did workers. Wasps were equally likely to groom thoraces or abdomens following heads, but were more likely to groom abdomens after thoraces and heads after abdomens. Interestingly, the appendages used to groom individual body parts were highly specific (e.g. the prothoracic legs were used for the head), thus indicating that grooming is not used to homogenize chemical cues across the body surface of the wasp.     

Queens of the Paper Wasp Polistes fuscatus (Hymenoptera: Vespidae) Discriminate among Larvae on the Basis of Relatedness

The ability of queens of the paper wasp Polistes fuscatus to recognize larvae on the basis of colony origin was investigated in the laboratory. In a blind, binary choice paradigm, queens discriminated between larvae from their own colony and unrelated larvae, and between larvae from a sister colony and unrelated larvae. However, queens failed to discriminate between larvae from their own colony and larvae from a sister colony, indicating that queens of multiple-foundress colonies may lack the ability to make intracolonial brood discriminations on the basis of relatedness. These results demonstrate that recognition of larvae is mediated by larval-borne, genetically specified odors. Gas chromatograph/mass spectral analysis revealed that adults and larvae have similar cuticular hydrocarbon profiles, suggesting that the cues mediating larval and adult recognition may be the same.     

Hilltopping Behavior of Polistes commanchus navajoe (Hymenoptera: Vespidae)

Males of the paper wasp Polistes commanchus aggregate in large numbers on hilltops in central and southeastern Arizona where individual males defend perch sites on shrubs, trees or rocks. Residents chase intruders away quickly and exhibit strong site fidelity at their perches. Takeovers are rare as are prolonged battles for possession of a site. Males have only weak preferences for peaktop perch sites as opposed to those lower on hillsides, and a similarly weak preference for perches in shrubs as opposed to those on rocks. Receptive females appear occasionally at the male aggregation sites to mate with perch holders. The relatively weak territoriality exhibited by P. commanchus may stem in part from the high density of males at peaktops and the correspondingly high rate of interactions. The evolution of hilltopping in a species whose reproductive females are clumped spatially at nest sites poses a puzzle for the ecological analysis of mating systems.     

Inhibition of Host Queen Reproductive Capacity by the Obligate Social Parasite Polistes atrimandibularis (Hymenoptera,Vespidae)

Polistes atrimandibularis is the obligate and permanent parasite of the social paper wasp Polistes biglumis bimaculatus. This parasite lives together with the host foundress for a considerable period on the invaded nest. Ovarian development was measured in females of the host species (foundresses and, when present, workers) from 18 parasitized and 14 non-parasitized colonies. The reproductive capacity of foundresses from parasitized nests decreased faster than that of foundresses from non-parasitized nests. These results indicate that the presence of the parasite lowers reproductive capacity of the host queen. Simultaneously, the fertility of the host worker is inhibited.     

Colony Development and Serial Polygyny in the Primitively Eusocial Wasp Belonogaster juncea juncea (Vespidae: Polistinae)

In Cameroon, the social ropalidiine wasp Belonogaster juncea juncea mostly selects human constructions for nesting, but nests installed in the shelter of large boulders were also noted. Nests were founded throughout the year by one female (25.5%) or by associations of two to eight females. Among the 49 colonies studied from foundation, 24 produced at least one adult, and only 5 produced males among the eight that succeeded in producing sexual individuals. After the first dominant female disappeared (died or abandoned the nest, from 77 to 196 days after foundation) the remaining females fought among themselves, leading to a drastic decrease in the total number of brood. They completely abandoned 22 of 24 surviving nests, over a mean colony cycle lasting about 7 months. Hence the colony and nesting cycles were congruent, illustrating that determinate nesting corresponds to the majority of the cases in this species. In the other two nests, some females remained on the nest and began a new colonial cycle illustrating semi-independence between colony and nesting cycles. Up to four successive cycles were completed in this way in the same nest, thus illustrating the phenomenon of serial polygyny (intermediate between determinate and indeterminate nesting cycles). Serial polygyny in independent founding polistine wasps, previously documented only once, has implications for studies attempting to identify factors involved in regulating the colony and nesting cycles in tropical social wasps.     

Polistes dominulus (Hymenoptera: Vespidae) larvae possess their own chemical signatures

Social insects use cuticular hydrocarbons (CHCs) as recognition cues in a variety of social contexts, such as species and nestmate recognition. Discrimination of nestmates is an important requisite to avoid exploitation by unrelated individuals. In social wasps, use of CHCs in nestmate recognition has been demonstrated only among adults, whereas very little is known regarding brood recognition. We performed gas chromatography-mass spectrometry analyses of the CHCs of adults and larvae of the social wasp Polistes dominulus and found that larvae possess a characteristic chemical colony-specific pattern distinct from that of adults. Behavioural assays confirmed that these are recognized and discriminated by adults. Larval epicuticular substances are therefore sufficient for recognition of nestmate larvae by adults and demonstrate that wasps are able to discriminate between alien and nestmate larval odours.     

Nesting Habit and Alarm Pheromones in Polistes gallicus (Hymenoptera, Vespidae)

Alarm pheromones are used in many social insects to elicit an alarm response of nestmates towards disturbances. This chemical alarm channel is especially used by species nesting in closed environments. Polistes gallicus paper wasps typically found their nests on open substrates where visual and vibrational stimuli could be more important than the chemical one to alarm the colony. We investigated, through field bioassays, if, also in this species, workers venom is still the source of alarm pheromones. Our results show that venom volatiles are able to increase the colony defence reaction stimulating more individuals to attack and sting the object of disturbance. Therefore our results suggest the hypothesis that chemical alarm is independent of nesting habit (concealed vs exposed) within the Polistes genus.     

Single-locus complementary sex determination in the inbreeding wasp Euodynerus foraminatus Saussure (Hymenoptera: Vespidae)

The Hymenoptera have arrhenotokous haplodiploidy in which males normally develop from unfertilized eggs and are haploid, while females develop from fertilized eggs and are diploid. Multiple sex determination systems are known to underlie haplodiploidy, and the best understood is single-locus complementary sex determination (sl-CSD) in which sex is determined at a single polymorphic locus. Individuals heterozygous at the sex locus develop as females; individuals that are hemizygous (haploid) or homozygous (diploid) at the sex locus develop as males. sl-CSD can be detected with inbreeding experiments that produce diploid males in predictable proportions as well as sex ratio shifts due to diploid male production. This sex determination system is considered incompatible with inbreeding because the ensuing increase in homozygosity increases the production of diploid males that are inviable or infertile, imposing a high cost on matings between close relatives. However, in the solitary hunting wasp Euodynerus foraminatus, a species suspected of having sl-CSD, inbreeding may be common due to a high incidence of sibling matings at natal nests. In laboratory crosses with E. foraminatus, we find that sex ratios and diploid male production (detected as microsatellite heterozygosity) are consistent with sl-CSD, but not with other sex determination systems. This is the first documented example of sl-CSD in a hymenopteran with an apparent natural history of inbreeding, and thus presents a paradox for our understanding of hymenopteran genetics.     

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.     

Social behaviour of the australian paper wasp,Ropalidia revolutionalis (de Saussure) (Hymenoptera: Vespidae)

Social behaviour ofRopalidia revolutionalis (de Saussure) was observed in Brisbane and Townsville. Nests were, as a rule, founded by association of females. Each nest began as a single comb but, after the emergence of progeny adults, satellite combs were constructed near the original comb. During the pre-emergence (single-comb) stage, each colony had a single egg-layer, despite the rare occurrence of intranidal dominance acts among female wasps. When colonies had reached the multiple-comb stage, the frequency and intensity of intranidal dominance-aggressive acts rose to a high level, comparable to those of typically aggressive colonies of e.g.Polistes canadensis in Panama. Colonies appeared to be still functionally haplometrotic during the early phase of multiple-comb stage, but several potential egg-layers were present as colony size increased. Dominant females often performed wing vibration, rapid runs between combs and tended to sit on the largest comb, whilst subordinate females tended to sit on smaller combs.