Biology of Tiphia pygidialis (Hymenoptera: Tiphiidae), a Parasitoid of Masked Chafer (Coleoptera: Scarabaeidae) Grubs, with Notes on the Seasonal Occurrence of Tiphia vernalis in Kentucky

We investigated the biology of Tiphia pygidialis Allen, a previously unstudied native parasitoid of masked chafer, Cyclocephala spp. grubs, in central Kentucky and the seasonal dynamics of Tiphia vernalis Rohwer, an introduced parasitoid of Japanese beetle, Popillia japonica Newman. T. pygidialis was active from mid-August to early October, parasitizing third-instar masked chafers, whereas T. vernalis attacked overwintered third-instar P. japonica frommid-April to early June. Adult T. vernalis were attracted to modiÞed Japanese beetle traps and yellow pan traps and to 10% sugar water sprayed on tree foliage. Spraying sugar water directly on turf most effectively monitored T. pygidialiswasps. Parasitism rates as high as 33 and 58%were observed for T. pygidialis and T. vernalis, respectively. In the laboratory,T. pygidialis larvae progressed throughÞve instars to cocoon formation in 22 d. They overwinter as prepupae. Field-collected female wasps lived 32 4 d, parasitizing 22 6 grubs. In no-choice tests with eight species of native and exotic white grubs, T. pygidialis readily parasitized only Cyclocephala spp., including C. lurida Bland and C. borealisArrow, which it normally encounters in Kentucky, but also C. pasadenaeCasey, a western species not know to occur within the waspÕs geographic range. Wasps did not discriminate between nematode-infected and healthy grubs, indicating potential for interference between these biological control agents.