Colony characteristics of Vespula germanica (F.) (Hymenoptera, Vespidae) in a Mediterranean climate (southern Australia)

Vespula germanica has been accidentally introduced into Australia, where it has now established as a horticultural, agricultural, environmental and nuisance pest. Despite comprehensive and often expensive eradication programs, remarkably little information exists for the species in Australia. Most previous Studies were conducted in its native range in England, and in New Zealand where V.germanica has also been introduced. Data on nesting sites in Adelaide were collected over two seasons, with a total of 2640 nests surveyed. The majority of nests (67%) were found below ground, mostly in soil. Twenty-nine percent of nests were found in artificial structures, while the remainder of nests was located above ground. Variation among different habitat types suggests that the species can utilise whatever nest sites are available. Colony duration, timing and seasonal development were also examined by collecting wasp nests over three seasons. Nests were found between November and May. Average mature colonies contained over 9500 small (worker) and 3600 large (queen and male) cells, with some large nests consisting of over 27 500 cells. By the end of May, such colonies have 15 000 wasps emerging from small cells and 2500 wasps emerging from large cells. This is 35-80% more than the numbers of adults produced by V. germanica colonies in England. In addition, in southern Australia a proportion of nests overwinter and Survive into the next season, whereas all nests collapse and die out at this time in England. A significant linear relationship was found between wasp traffic and various measures of nest size. These results indicate that in the absence of an adverse climate, V. germanica nests can attain a substantial size. Greater numbers of queens produced in nests may also facilitate a faster rate of population increase in Australia.