Further Studies of Field Parasitism of the Face Fly1 by the Nematode Heterotylenchus autumnalis2 in Central Missouri, with Notes on the Gonadotrophic Cycles of the Face Fly3

Abstract

Parasitism of Musca llutumnalis De Geer by the nematode Heterotylenchus autum- nalis Nickle was investigated at 2 farms in central Missouri during 1970. Mean seasonal parasitism at the 2 farms averaged 33.5 and 26.2%, whereas face fly populations aver- aged 7.4 and 8.7/head of cattle, respectively. Five methods of sampling face flies to measure parasitism by the nematode were evaluated. Parasitism was significantly higher in flies collected from the surface of manure pats than those collected from either the sides of a truck or the faces of the cattle, Most unparasitized flies (94.2%) had undergone only 2 gonadotrophic cycles. Also, a majority of the unparasitized flics collectcd from the manure pats (61.3%) contained mature eggs, whereas only 17.1 % of those collected from the truck and the faces of the cattle had mature eggs.