Adaptive nesting tactics in a paper wasp, Polistes riparius, inhabiting cold climatic regions

Abstract

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. In ter-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. These results 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.