Nestmate discrimination in social wasps (Polistes metricus,Hymenoptera: Vespidae)

Summary Laboratory-overwintered paper wasp (Polistes metricus) females preferentially associate on new nests with former nestmates (presumably their sisters) rather than with non-nestmates in the absence of cues associated with their natal nests or nest sites. Females isolated from conspecifics and nests for 74–99 days retain the ability to discriminate nestmates from nonnestmates.     

Discrimination between nestmate and non-nestmate kin by social wasps (Polistes fuscatus,Hymenoptera: Vespidae)

Summary The threespine stickleback,Gasterosteus aculeatus is a voracious cannibal of both its own eggs and those of conspecific neighbours. Females, but not males, can distinguish their progeny from those of other fish and attacked alien eggs more frequently. In experiments to examine nest raiding, females that initiated raids on nests resulting in cannibalism were the first females to spawn in the reconstructed nest. These results support the hypothesis that cannibalism by females may be adaptive in situations where intense female competition for male guardians occurs.     

Recognition of former nestmates during colony founding by the social wasp Polistes fuscatus (Hymenoptera: Vespidae)

Summary In the laboratory overwintered females of Polistes fuscatus preferentially associated with former nestmates during the founding of a colony. They did not associate with non-nestmates or only with nestmates with whom they had overwintered, but affiliated with all former nestmates, regardless of where the former nestmates overwintered.     

Colony activity integration in primitively eusocial wasps: the role of the queen (Polistes fuscatus,Hymenoptera: Vespidae)

Summary The queen's role in colony activity integration in small post-emergence colonies of Polistes fuscatus was investigated in the field. We continuously recorded the behaviors of all wasps in (1) undisturbed colonies, (2) colonies from which the queen had been removed, (3) colonies from which a single worker had been removed, (4) colonies with a cooled, relatively inactive queen, and (5) colonies with a cooled, relatively inactive worker (29 colonies; 148 h observation).The queen spends more time on the nest, spends more of its nest time active, participates in more interactions/h, and initiates more interactions/h than does the average worker. Overall, the queen is involved in more interactions than is any other colony member. Queen removal depresses worker activity level and causes episodes of worker activity to become less temporally coupled (less synchronized).The presence of a cooled, inactive queen on the nest produces an even greater reduction in worker activity level and also results in decreased synchrony in worker activity episodes. Removal or cooling of a single worker produces no systematic changes in the activities of the other colony members. We conclude that the P. fuscatus queen is a central pacemaker and coordinator of colony activity.     

Nestmate recognition in three species of stenogastrine wasps (Hymenoptera,Vespidae)

The capacity to recognise a conspecific intruder was investigated in Parischnogaster jacobsoni, Liostenogaster flavolineata and L. vechti, three species of primitively social wasps of the subfamily Stenogastrinae. Results of behavioural experiments carried out in the field showed that females of all three species react pacifically if presented with female nestmates, but aggressively reject an intruder from a conspecific colony. As L. flavolineata and L. vechti both build large clusters of nests, often very close to each other, the recognition capacity among females from different nests, but in the same conspecific cluster, was also investigated. Females of both species were more aggressive towards females from a different colony in the same cluster than towards their female nestmates. Additional experiments on L. flavolineata showed that there was no difference in reaction towards females from colonies nearer or further from the tested colony but within the same cluster, nor towards females from a different cluster. The capacity to recognise an alien conspecific nest containing immature brood was investigated in P. jacobsoni. Adult females of this species, invited to land on an alien nest which had experimentally been exchanged for their own, accepted the new nest and partially destroyed the immature brood. The behaviour of the females when they land on an alien nest, however, suggests that they do recognise the nest as foreign. Acceptance of foreign nests coupled with low immature brood destruction is probably due to the high energetic costs of egg-deposition and larval rearing in stenogastrine wasps. These results suggest that nestmate recognition in these wasps is very efficient, even though they belong to the most primitive subfamily of social wasps. Received: 16 April 1996/Accepted after revision: 9 August 1996     

Alternative mating tactics in males of Polistes dominulus (Hymenoptera: Vespidae)

Summary In summer, males of Polistes dominulus form large aggregations at sunny landmarks. We identified two size-correlated behavioural categories: residents (R) and transient (T). R males, which constitute 20%–25% of the total population, are larger than T males, territorial, aggressive, and more site-faithful, while T males range more widely, are non-aggressive, and show little site tenacity. Field and laboratory data suggest that R males have an advantage in mating, particularly if they engage in frequent flights while on their territories. These alternative mating tactics within the same population are combined with behavioural flexibility in some individuals, which switch from one option to the other.     

Relatedness among nestmates in a primitively social wasp,Cerceris antipodes (Hymenoptera: Sphecidae)

Summary Kin selection, acting through high levels of relatedness, may be an important promoter in the evolution of nest sharing. Cerceris antipodes is a sphecid wasp that shares nests in contrast to the majority of sphecids where only one female occupies a nest. Nest sharing results from females remaining in their natal nests and females moving to already occupied nests. Average relatedness among nestmates of C. antipodes was calculated from allele frequencies of phosphoglucomutase to determine whether nests were usually shared by close relatives. Relatedness among nestmates was high (0.5 to 0.6) at one aggregation in two consecutive years. Preferential association of relatives away from the natal nest can be inferred from these high values combined with the frequency of nest switching observed. Estimates of relatedness were lower (about 0.3) and associated with large standard errors at 3 other aggregations. Inbreeding and relatedness between neighbouring nests were only significant at the aggregation with the fewest females. This may be a result of the small effective population size. The levels of relatedness observed are consistent with kin selection through relatedness being an important factor in the evolution of nest sharing.     

Effects of stage of colony cycle,context, and intercolony distance on conspecific tolerance by paper wasps (Polistes fuscatus)

Summary We observed in the field how resident females of the social wasp, Polistes fuscatus, treated female nestmates, non-nestmate first cousins, and unrelated non-nestmates. Behavioral observations were made 1, 3, 4, 6, 7, 8, and 11 weeks after the emergence of a colony's first workers. Resident females were highly tolerant of female nestmates but highly intolerant of unrelated non-nestmates throughout the post-worker-emergence phase of the colony cycle. First cousins were treated either highly tolerantly or highly intolerantly, although most cousins ( 63%) were treated highly intolerantly. The treatment of cousins suggests that they are treated either tolerantly (like nestmates) or intolerantly (like unrelated non-nestmates) depending on whether they fall above or below an acceptance threshold, respectively. Resident females did not significantly change their tolerance nestmates, first cousins, and unrelated females between different observation periods. However, all conspecifics were generally treated the most intolerantly 11 weeks post-worker-emergence, a time in the colony cycle when combs no longer contain brood. This decreased tolerance and its associated variance patterns late in the colony cycle are consistent with a more restrictive acceptance threshold. The optimal level of the acceptance threshold appears to be a compromise between the fitness consequences of accepting unrelated non-nestmates and rejecting one's nestmates. In a laboratory study, resident females were equally tolerant of female nestmates on and off the comb but significantly less tolerant of unrelated females on the comb than off the comb. Thus, females can modify their tolerance rapidly in different recognition contexts. In a second laboratory study, resident females were equally intolerant of unrelated females, regardless of whether they were from colonies 50 m or 50 km distant.Offprint requests to: G.J. Gamboa     

Forager specialization and the control of nest repair in Polybia occidentalis Olivier (Hymenoptera : Vespidae)

We measured patterns of individual forager specialization and colony-wide rates of material input during periods of response to experimental nest damage and during control periods in three colonies of the tropical social wasp Polybia occidentalis.

Behavioural evidence for the involvement of Dufour’s gland secretion in nestmate recognition in the social wasp Polistes dominulus (Hymenoptera: Vespidae)

The results of recent studies by our group have suggested that in social wasps of the genus Polistes the Dufour’s gland is involved in kin recognition. In fact, the same hydrocarbons occurring on the cuticle are found in the gland secretion, and in P. dominulus the composition of the glandular secretion is more similar in foundresses belonging to the same colonies than in heterocolonial foundresses. In this study, P. dominulus colonies were experimentally presented with previously treated dead conspecific females. These lures had been deprived of their epicuticular lipids and coated with epicuticular or Dufour’s gland secretion extracts from females hetero- or homocolonial with respect to the tested colonies. The behaviour of the colonies towards these lures indicates that, like the epicuticular lipids, the Dufour’s gland secretion is involved in nestmate recognition. Received: 14 August 1995/Accepted after revision: 5 November 1995     

Hibernation clustering and its consequences for associative nest foundation in<Emphasis Type="Italic"> Polistes dominulus</Emphasis> (Hymenoptera Vespidae)

Various studies indicate that cuticular hydrocarbons (CHCs) act as cues for nestmate recognition in paper wasps and other social insects. A recent study showed that associative nest foundation in Polistes dominulus is mainly performed by foundresses coming from the same locality. In the present study, we induced future foundresses of P. dominulus collected in two different localities to hibernate in the laboratory in aggregates of individuals from the same or different localities. After 2 months of hibernation, foundresses from different localities but from the same experimental cluster did not show any preference to associate, at the time of nest foundation, with individuals coming from the same original locality. The cuticular chemical profiles of individuals from the mixed hibernation clusters were quite similar and significantly different from those of individuals which hibernated with other foundresses from the same locality. These findings suggest that, in this species, mechanisms other than nestmate chemical recognition play a major role in the spring association of gynes during the foundation of a new nest.Communicated by R.F.A. Moritz     

Shifting foraging strategies in colonies of the social wasp Polybia occidentalis (Hymenoptera, Vespidae)

Social insect colonies can be expected to forage at rates that maximize colony fitness. Foraging at higher rates would increase the rate of worker production, but decrease adult survival. This trade-off has particular significance during the founding stage, when adults lost are not replaced. Prior work has shown that independent-founding wasps rear the first workers rapidly by foraging at high rates. Foraging rates decrease after those individuals pupate, presumably reducing the risk of foundress death. In the swarm-founding wasps, colony-founding units have many workers, making colony death by forager attrition less likely. Do swarm-founding wasps show similar shifts in foraging rates during the founding stage? We measured foraging rates of the swarm-founding wasp, Polybia occidentalis at four stages of colony development. At each stage, foraging rates correlated with the number of larvae present, which, in the founding stages, correlated with the number of cells in the new nest. Thus, foraging rates appear to be demand-driven, with the level of demand in the founding stage set by the size of nest that is constructed. During the founding stage, foraging rates per larva were high initially, suggesting that colonies minimize the development times of larvae early in the founding stage. Later in the stage, foraging rates decreased, which would reduce worker mortality until new workers eclose. This pattern is similar to that shown for independent-founding wasps and likely results from conflicting pressures to maximize colony growth and minimize the risk of colony death by forager attrition.     

The role of trail pheromones in host nest recognition of the social parasitic bumblebees Bombus bohemicus and Bombus rupestris (Hymenoptera: Apidae)

Bumblebees of the subgenus Psithyrus are obligate social parasites of Bombus colonies. Parasitic females enter host colonies and replace the host queen. The offspring of the parasite is reared by the host workers. Females locate host colonies by nest searching flights and recognition of species-specific nest odours at the entrance. We investigated inter- and intraspecific odour variation of 45 hydrocarbons of nests of potential hosts by coupled gas chromatography/mass spectrometry and tested the preferences of the parasite females of B. bohemicus and B. rupestris for these mixtures in Y-olfactometer choice tests. Interspecific and intracolonial differences in the odour bouquets of the host species were found to be predominantly due to different patterns of alkenes. Furthermore, we found intercolonial differences within the single species. In behavioural assays, females of the two species showed different preferences for the offered nest odours, implicating different host spectra. Bombus rupestris showed a clear preference for the scent of its host, B. lapidarius. Bombus bohemicus females were attracted by B. terrestris, B. lucorum, and B. cryptarum in a similar manner. The results show that volatile signals enable parasite females to discriminate between potential host species.     

Predatory behavior of Polybia sericea (Olivier), a tropical social wasp (Hymenoptera: Vespidae)

Summary Polybia sericea (Olivier) (Hymenoptera: Vespidae) foragers were trained to visit experimental foraging plots and tests were conducted to determine the role of visual, olfactory, and chemotactile cues in prey location. Foragers approached prey from downwind and hovered downwind of visual and olfactory stimuli. Olfactory cues were more likely to elicit landing than were visual cues. Biting of potential prey was most consistently elicited by a combination of visual, tactile, and chemotactile cues. Foragers encountering large prey carried a piece back to the nest and returned for prey remains. These returning foragers used visual cues to direct intensive aerial search; olfactory prey cues elicited landing.     

Genetic relatedness of worker nestmates in Myrmica ruginodis (Hymenoptera : Formicidae) populations

Summary Genetic relatedness and mating structure of the red ant, Myrmica ruginodis, were studied from a large data set in several natural populations, one of which was a substructured archipelago population. Within-colony relatedness of worker nestmates was measured as genotypic correlation and mating structure as deviation from random mating; both were calculated from the genotype frequency data. The average relatedness of worker nestmates was rather high across populations (0.43–0.73), and random mating was the rule within populations. The data were used to deduce the social structure of populations. With one possible exception, populations turned out to be weakly polygynous, implying that they consisted of the macrogyne form of the species. The exceptional population was relatively more polygynous and inbred, suggesting that it might include the microgyne form. This exceptional population lived in a habitat not noticeably different from that of the other populations, challenging previous suggestions of the habitat specialization of the two forms. The colonies were facultatively polygynous, and a comparison with earlier studies shows that polygyny is functional. Relatedness of worker nestmates varied slightly among populations, indicating that the social structure of Myrmica colonies is flexible.     

Dominance and polyethism in the eusocial wasp Mischocyttarus mastigophorus (Hymenoptera: Vespidae)

Dominance interactions affected patterns of non-reproductive division of labor (polyethism) in the eusocial wasp Mischocyttarus mastigophorus. Socially dominant individuals foraged for food (nectar and insect prey) at lower rates than subordinate individuals. In contrast, dominant wasps performed most of the foraging for the wood pulp used in nest construction. Social dominance also affected partitioning of materials collected by foragers when they returned to the nest. Wood pulp loads were never shared with nest mates, while food loads, especially insect prey, were often partitioned with other wasps. Dominant individuals on the nest were more likely to take food from arriving foragers than subordinate individuals. The role of dominance interactions in regulating polyethism has evolved in the eusocial paper wasps (Polistinae). Both specialization by foragers and task partitioning have increased from basal genera (independent-founding wasps, including Mischo-cyttarus spp.) to more derived genera (swarm-founding Epiponini). Dominance interactions do not regulate forager specialization or task partitioning in epiponines. I hypothesize that these changes in polyethism were enabled by the evolution of increased colony size in the Epiponini. Received: 8 December 1997 / Accepted after revision: 28 March 1998     

Trail discrimination signal of Lasius japonicus (Hymenoptera: Formicidae)

Summary. Trail-following behavior of Lasius japonicus was colony-specific in the field, while trail pheromone activity was not. We found that the footprint substance caused colony-specific trail-following behavior only when working in conjunction with the trail pheromone. The footprint substance alone did not lead the workers to follow trails. The substance consisted mainly of hydrocarbons with composition almost identical to that of cuticular hydrocarbons, except for the absence of n-alkanes. Nestmate workers shared footprint hydrocarbon profiles as well as cuticular hydrocarbons, but the profiles differed among colonies. We therefore consider that the footprint hydrocarbon profiles serve as the trail discrimination signal in L. japonicus.     

Parental investment in two solitary wasps Ancistrocerus adiabatus and Euodynerus foraminatus (Eumenidae: Hymenoptera)

Summary Females of the solitary eumenid wasps Ancistrocerus adiabatus and Euodynerus foraminatus control the adult size of their offspring by the amount of food provded to the larvae. For both species, larger females provision more offspring and collect more food than smaller females. Males of E. foraminatus, upon emergence as adults, fight for control of the nest area. The winning brother remains at the nest and mates with his sisters as they emerge several days later. Males of A. adiabatus are not as agonistic as males of E. foraminatus so that a number of males may remain near the natal nest. When females nest near each other, male-male interactions increase, and the likelihood of sibling mating decreases. Under conditions of clumped nesting, females make larger offspring and invest more in males than when nesting in isolation.