Oviposition and Wound-Visiting Behavior of the Screwworm Fly, Cochliomyia hominivorax (Diptera: Calliphoridae)

Abstract

Female screwworm flies, Cochliomyia hominivorax (Coquerel), visit wounds of warm-blooded animals to feed and oviposit, with feeding visits occurring twice as often as oviposition visits. Feeding visits average 5.4 min and oviposition visits average 15.4 min, but both types of visit may last up to 1 h. Screwworms are iteroparous, with oviposition occurring in a 3-d cycle. One female fly was recorded to live 33 d and oviposited at least eight times. Oviposition activity by the population followed a 17–19-d cycle, which probably corresponds to the life cycle of the fly. Clutch size is variable from 28–492 eggs, with a mean of 200 eggs per clutch. Females deposit their clutch in one to four masses of eggs, usually on the margin of a wound. If a wound is preoccupied by an egg mass, an ovipositing female places her egg mass on top of or in direct contact with the previous egg mass most (67%) of the time. Thus, the presumption of one egg mass equalling the reproductive output of a single female is invalid. Female screwworms combine longevity and iteroparity with autogeny and large clutches. This reproductive behavior is well adapted for exploitation of a transitory resource such as wounds on living animals.