Polistine Wasps and the Colony Cycle

olistine Wasps

Colonies of Polistine wasps are composed primarily of females; males are produced only for mating purposes. Colonies include queens, the principal egg layer in the colony, gynes, females that will become a queen in the following year, foundresses, mated females capable of laying eggs in a spring nest, and workers, females who work on their natal nest and have the potential to become queen. A female wasps role is not predetermined; when a females emerges from her cocoon, she has the potneial to become a queen or a worker. Her final role in the colony depends on the status of the colony cycle and on a number of other social factors.

he Colony Cycle

Colonies are started in the spring by mated, overwintered females that emerge from their hibernation sites on warm days. While single females sometimes start a colony, often times a group of females will found a colony together. This group of females must fight amongst themselves to establish a dominance hierarchy. The female at the top of the hierarchy becomes the queen, while the rest of the foundresses start to function as workers. The ovaries of the queen become well developed and she turns into the main egg layer. The ovaries of the rest of the foundresses start to decrease in size as they take on the dangerous tasks of foraging for water, for plant fibers to construct the nest, and for nectar and caterpillars to feed the queens and her offspring.

The foundress or foundresses raise a generation of offspring, which, upon emerging as adults, become workers. If there is enough time before the end of the season, the workers help raise more workers. If not, they will help raise a generation of females that will mate and hibernate to become foundresses the next spring. A generation of males is also produced by the end of the year. They will mate with the future foundress and, along with the workers, will die over the course of the winter.

eviations from the Colony Cycle

The shortness of the growing season of northern climates leaves little room for deviation from the general colony cycle. However, in populations with extended growing seasons, it is more likely for the structure of the colony to change over the course of the season. Drastic changes may result from the destruction of the nest by predators such as raccoons or birds. Ants frequently raid nests and take all the brood for food. As well, parasites often infest the larvae and pupae causing irreparable damage to the brood. These factors often make it difficult for colonies to reach the end of the nesting cycle to produce the future reproductives, and cooperative work becomes an essential factor in recuperating from such events.

Outside factors, such as parasites and predators, have an extensive effect on a colony. However, drastic changes to the hierarchic structure of the colony may result from conflicts of interest within the colony itself. For example, when the queen dies, one of the co-foundresses or one of the workers takes over the queen's position. Due to the varying genetic relatedness of the different females, the takeover leads to a conflict of interest between workers and foundresses. Part of this project will be to determine who you believe will take over.

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