Seasonal Changes in the Population Structure of Wasp Colonies (Hymenoptera: Vespidae)

Total counts and estimates of the populations of wasp colonies have been made by several authors (e.g. Weyrauch 1935; Richards & Richards 1951; Blackith & Stevenson 1958; Kemper 1961; and Kemper & Dohring 1961) and their population dynamics have been discussed by Bodenheimer (1937) and Brian (1965). The only information about seasonal changes in vespine colonies is a little on hornets by Janet (1895), Ishay (1965), and by Ishay, Bytinski-Salz & Shulov (1968). This paper describes the populations in colonies of Vespula vulgaris (L.) and V. germanica (F.). In 1961, fifty-nine colonies of V. vulgaris and thirty colonies of V. germanica were collected within a 10 km radius of Rothamsted Experimental Station. A further twenty-three colonies were discovered but not sampled. Colonies were killed at intervals during the season with dieldrin or chloroform. Returning wasps that remained outside the nest overnight were caught. The combs, cells, immature stages and adults were counted in each nest, and the number of generations of wasps produced per cell was determined by counting the faecal pellets in each. Cells were measured with calipers. In each foundress queen, the six pairs of ovarioles were examined; and in each ovariole the number of eggs equal in size to, or larger than, the nurse cells ('ovariole index', Cumber (1-949)) was determined. V. germanica adults collected in suction traps at Rothamsted during 1960-61 (Taylor 1963) were also examined.