Adaptive Nesting Tactics in a Paper Wasp, Polistes riparius, Inhabiting Cold Climatic Regions

Thermal effects on the nest sizes constructed by Polistes riparius foundresses, their nesting activities, and colony compositions were determined in laboratory conditions during the pre-emergence period. In this study, foundresses were placed in cold (20°C) and warm conditions (27°C), and ample food and nest materials were supplied. Nest sizes were larger in the cold condition; particularly, the elongation of cells was remarkable. The number of cells between the 2 conditions was not significantly different. Inter-condition colony composition was similar, while more honey drops were observed in the cold condition nests. A positive relation was observed when the relationships between body weight and developmental days were investigated, i.e., small offspring required shorter developmental days in both thermal conditions. In the cold condition, the first offspring were very small, whereas offspring size increased steeply after the second order, and was comparable to that of the foundresses; the size increase in the warm group was slight. This result indicates that the cold condition foundresses manipulated the sizes of their offspring. When inter-condition foundresses activities were compared , cold condition foundresses spent more time and energy on flight activities. Theseresults support the view that foundresses change nesting activities in relation to environmental temperatures, i.e., they can improve the thermal condition of nests by adding extra cells and manipulate the sizes of adult offspring

Seasonal cycle of the nest composition in the Ponerine ant Cryptopone sauteri (Hymenoptera: Formicidae)

The annual life history is a basic and important factor in ecological studies on temperate ant species. The biology of Ponerinae species has been studied for many species, but little attention has been paid to their life history. Cryptopone sauteri is one of the most common ants in temperate regions of Japan. However, there is no quantitative information on the life history of this species. We report seasonal changes in brood development, the emergence of reproductives and social structures of C. sauteri. Additionally, we discuss that this species possibly exhibits a polydomous nesting system

Ambient Temperature Influences Geographic Changes in Nest and Colony Size of Polistes chinensis antennalis Pérez (Hymenoptera, Vespidae)

In some Polistes wasps, the foundresses build huge nests during the founding phase to improve the thermal condition of nests. This implies that Polistes wasps change their nesting manner in relation to ambient temperature. To test the hypothesis that nest size increases with latitude, colonies of Polistes chinensis were collected from 11 locations. Three nest parameters, the number of cells cell length and index of functional envelope, increased with latitude. The number of cells at the northernmost station was 60, which was 1.5 times more than in lower latitudes. Cell length increased by approximately 4 mm from low to high latitudes, indicating that extra-building in P. chinensis is remarkable in adding new cells. The number of first broods was not correlated with latitude, whereas the number of second brood increased with latitude because of the numerous cells built at high latitudes

The acceptance rate of young wasps by alien colonies depends on colony developmental stages in the swarm-founding wasp, Polybia paulista von ihering (Hymenoptera: Vespidae)

In social insects, newly emerged individuals learn the colony-specific chemical label from their natal comb shortly after their emergence. These labels help to identify each individual's colony of origin and are used as a recognition template against which individuals can discriminate nestmates from non-nestmates. Our previous studies with Polybia paulista von Ihering support this general pattern, and the acceptance rate of young female and male wasps decreased as a function of their age. Our study also showed in P. paulista that more than 90% of newly emerged female wasps might be accepted by conspecific unrelated colonies. However, it has not been investigated whether the acceptance rate of newly emerged female wasps depends on colony developmental stage of recipient colonies. We introduced newly emerged female wasps of P. paulista into different colony developmental stags of recipient colonies, i.e., worker-producing and male-producing colonies. We found that the acceptance rate of newly emerged female wasps by alien colonies was pretty lower by male-producing colonies than worker-producing colonies. This is the first study to show that the acceptance rate of young female wasps depends on stages of recipient colonies

Presence of Strepsiptera Parasites in the Independent-founding Wasp, Polistes satan

Although the paper wasp genus, Polistes, has been examined extensively, little is known about the occurrence of parasitism in this group. We detected the obligate parasitic insect group, Strepsiptera in the gaster of Polistes satan Bequaert adult females. By dissecting 161 adult females from 24 colonies, we identified a total of four stylopized wasps in three colonies during the wet season.

Polymorphic Microsatellite Loci in the Independent-founding Wasp Polists versicolor (Hymenoptera: Vespidae)

Microsatellite primers developed for a given species are sometimes useful for another in the same genus, making possible to search for pre-existing suitable primers in the data banks such as GenBank. We examined whether existing primers developed for Polistes wasps could be used for the independent-founding wasp Polistes versicolor. We tested 50 microsatellite primers from three Polistes species and found that five microsatellite loci show polymorphism in size in P. versicolor. These five loci were highly polymorphic, having four to 10 alleles in P. versicolor with an expected heterozygosity of 0.530–0.836. 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

Nest thermoregulation in Polybia scutellaris (White) (Hymenoptera: Vespidae)

Polybia scutellaris (White) builds large nests characterized by numerous spiny projections on the surface. In order to determine whether or not the nest temperature is maintained because of homeothermic conditions of the nest individuals or otherwise, we investigated the thermal conditions within the nests built by P. scutellaris. We measured the temperature within active and abandoned nests. The temperature in the active nest was almost stable at 27°C during data collection, whereas the temperature in the abandoned nest varied with changes in ambient temperature. These results suggest that nest temperature was maintained by the thermogenesis of the individuals of the colony. This is the first report of nest incubation caused by thermogenesis of species of Polybia wasps

Levels of parasitism of Xenos myrapetrus (Stresiptera, Stylopidae) and its seasonal changes in the swarm-founding wasp, Polybia paulista (Hymenoptera, Vespidae)

Social insects face strong selection from parasites because the conditions of group living often favor the transmission of infection among nestmates. Yet, we lacked detailed information on the effect of parasite infection in the host species. Workers of Polybia species, Neotropical swarm-founding wasps, are commonly infected by strepsipteron, possibly Xenos myrapetrus (Trois). Previous studies showed in two Polybia species that workers infected by the strepsiptera were smaller than uninfected workers. However, the effect of seasonality on infection rates throughout a year or between wet and dry seasons has not been examined. We compared rates of strepsiptera infection in workers of Polybia paulista between wet and dry seasons or among months. Infection rates by the strepsiptera in workers are generally low throughout a year, but different between the seasons. However, there is no particular tendency on seasonal differences of workers infected by the strepsiptera. Population dynamics of the parasites and temperature variation can have effects on the differences