Effects of Larval Competition on Face Fly 1

Abstract

Laboratory and field studies assessed how face fly, Musca autumnalis DeGeer (Diptera: Muscidae), was affected by competition among fly larvae for cattle dung. Cohorts of 1st-instar face flies were reared with known amounts of dung per individual, and then various life-history attributes of the larvae and subsequent stages were examined. The 1st symptom of competition was stunting of subsequent pupae and adults. Stunted females emerged earlier, matured later, possessed fewer ovarioles and were less fecund than their full-sized counterparts. Where competition was intense, few larvae survived to pupate, and the majority of the pupae died before adults emerged. The intensity of competition did not affect the sex ratio and longevity of flies that survived to adult. Field data corroborated the relationship between the density of coprophagous fly larvae and the size of emerging female face flies. These results indicate that competition may or may not be detected within the coprophagous guild, depending upon which life-history attributes of the suspected competitors are analyzed.