Phenology and population structure of annual nests of the German wasp Vespula germanica (Fab.) in Manawatu, New Zealand, with particular reference to late summer and autumn

Abstract

Annual nests of the German wasp Vespula germanica were collected in Manawatu between January and May, 1969–1988, and analysed as a single cohort Most nests were from urban locations, and subterranean nests were selected preferentially. The study is a baseline measure of a German wasp population in the absence of common wasps. Given the rapid spread of common wasps this circumstance may never be repeated on mainland New Zealand.

Manawatu colonies reach peak numbers between mid and late April. Drones are most numerous in mid April and queens in late April to early May. Nests taken in the same locality on the same day vary demographically; large nests generally hold higher proportions of reproductives than small nests.

Manawatu nests are generally larger and have more combs than those in England. The area and number of combs increases steadily from January to May. Complementary seasonal changes in the total area of pupal cells, and of empty cells plus cells with eggs, support the view that colonies achieve maximum size in mid to late April. The total area of larval cells remains fairly stable from January to May, as does the larva: worker ratio between mid February and early May.

Urban and rural colonies follow the seasonal pattern for Manawatu, but urban nests are larger than rural ones, produce more workers and reproductives (including earlier drones), have more combs, and hold more larvae. The caution is given that in Manawatu it may be spurious to sharply divide urban and rural nests because in some areas these habitats are closely interwoven. Nest production is also possibly affected by the nature of the nest site.

Attention is drawn to the need for future work to clarify the complex of effects of habitat, nest site, and regional climate on wasp phenology and demography. Closer targeting of control measures would follow.

Keywords:

• Phenology
• population structure
• wasps
• Vespula germanica
• German wasp
• Manawatu
• nests
• demography