Seasonal and Relative Abundance of Hymenopterous Parasitoids Attacking House Fly Pupae at Dairy Farms in Central New York

Abstract

A survey of indigenous parasitoids attacking Musca domestica L. and Stomoxys calcitrans (L.) pupae was conducted for 2 yr at eight dairies by exposing weekly samples of laboratory-reared fly pupae (sentinel bags). Mean relative abundance of each species was 59% Muscidifurax raptor Girault and Sanders, 14% Urolepis rufipes (Ashmead), 11% Phygadeuon fumator Gravenhorst, 10% Spalangia cameroni Perkins, 3% Spalangia nigroaenea Curtis, and 2% Trichomalopsis dubius (Ashmead). Rare species included Pachycrepmdeus vindemmiae (Rondani), Nasonia vitripennis (Walker), Dibrachys cavus (Walker), Spalangia nigra Latreille, and Macroneura vesicularis (Retzius). Total parasitism was phenologically synchronized with the house fly population occurring between 17 May and 27 October, but it peaked 1–2 mo after the fly population peaked. M. raptor, U. rufipes , and P. fumator were common in June. A decrease in parasitism by M. raptor and U. rufipes during late July may represent a gap between the first two generations. Paired samples of sentinel house fly and stable fly pupae indicated no difference in parasitism by M. raptor or by all species combined. However, U. rufipes parasitized more house fly pupae, and P. fumator parasitized more stable fly pupae.