Some Relationships of Face Fly Feeding, Ovarian Development, and Incidence on Dairy Cattle12

Abstract

Feeding behavior, ovarian development, and incidence of the face fly, Musca autumnalis De Geer, on the faces of dairy cattle were studied. Although some field-collected flies were observed, most of the studies used flies from a laboratory culture maintained at the Ohio Agricultural Research and Development Center, Wooster. The flies in the culture were held at approximately 80°F and 50% relative humidity and were provided with a diet of malt, non-fat dry skim milk, citrated bovine blood, water, and fresh bovine feces. Feeding responses were tested in the laboratory by exposing the flies to a free-choice diet and examining the contents of the digestive tract at regular intervals to determine the food consumed. Males and females 1-6 days old differed in their feeding responses. Males showed little variation in daily feeding and fed primarily on malt. Females 1-13 days old showed cyclic feeding responses—feeding on significantly greater amounts of blood and milk at 3 days of age, and dung at 4 and 6 days. Peak levels of feeding were observed for blood at 3 and 8 days and for dung at 4, 7, 10, and 13 days. Ovarian development was studied by observing the growth of ovaries and oocytes, times of oviposition, and levels of ovarian development in field-collected females. Ovarian development was cyclic in females 1-12 days old. Peak oocyte length was observed in females 5 and 10 days old, and peak oviposition in females 5 and 11 days old. Incidence on the faces of dairy cattle, by 1- to 12-dayold females, was studied by field release of 19,345 specimens tagged with fluorescent dusts. Incidence varied in a cyclic pattern with age, the highest incidence was observed in females 3 and 8 days old. Certain temporal relationships among feeding, ovarian development, and incidence on the faces of dairy cattle were evident in laboratory-reared female face flies 1-12 days old. The females alternately fed on blood and then completed gonadotrophic cycles. Peak blood feeding and peak incidence on dairy cattle were closely related. Peak dung feeding occurred 1 day before and 2 days after each oviposition peak. The females alternated between the completion of gonadotrophic cycles and incidence on dairy cattle. Levels of ovarian development in field-collected females supported the existence of this latter alternation. Differences in incidence on the faces of dairy cattle were attributed to differences in the feeding responses of the female flies. Differential feeding responses were attributed to the nutritional requirements of cyclic egg maturation.