Nesting Biology and Taxonomy of Arpactophilus-Mimi, a New Species of Social Sphecid (Hymenoptera, Sphecidae) From Northern Australia

Abstract

Arpactophilus mimi, Naumann, sp. nov., is described from Kakadu National Park, N.T. and its biology is outlined. A. mimi nests in abandoned cells of mud-dauber wasps in sandstone overhangs. Its nests are lined heavily with silk and contain 1-15 cells and 1-10 adult wasps (1-7 females, 0-3 males). On average nests contain 5.2 cells and 2.75 adult females. Prey (immature Psyllidae and Tingidae) are supplied progressively. Nests are parasitised by a species of megalyrid wasp, but incidence of parasitism is low. Nest defense is both physical (entrance guard always present) and chemical (citrus odour from heads of both sexes). Females from a single nest could be ranked on the basis of relative ovarian development, suggesting that more than one female oviposits. Females apparently cooperate in brood care and offspring in a nest develop asynchronously. The biology of A. mimi is compared to that of Microstigmus comes Krombein, the most socially advanced sphecid known, and selective pressures that may have acted to promote female cooperation in the two genera are discussed. For A. mimi the lack of available nest sites could be an important factor restricting the ability of offspring to disperse and establish nests.