Field notes on the occurrence of Hemithynnus hyalinatus (Hymenoptera : Tiphidae) as a parasite of scarabaeids on the New England Tablelands

Hemithynmus, hyalinatus Westwood, a wasp parasite of scarabaeid larvae in the New England Tablelands area, is associated with persistent populations of its potential host species which have a discontinuous distribution in the area. Of the larger insects in the soil sampled at one field site from 1964–1968, 77% were Scarabaeidae, 15% Thynninae, 7% predators and 1% hyperparasites. Wasp mortality in the field was only measured for stages in the cocoon; of these 5% were killed by a rhipiphorid and 12% were diseased. The depth of the cocoon affected its susceptibility to attack. The observations suggest that the numbers of H. hyalinatus may be related to the density of the host. However, there is no evidence that the parasites exert an important controlling influence on scarabaeid populations.