Alternative to Sentinel Animals for Collecting Egg Masses from Wild Females of the Screw worm (Diptera: Calliphoridae)

Egg masses from wild populations of the screwworm, Cochliomyia hominivorax (Coquerel), were obtained by collecting females from rotted liver, holding them for 3 d until egg maturation and then placing them on heated ground beef for oviposition. Nearly 50% of the females oviposited. Fertility of egg masses was 66 and 95% at the two collection sites. Decreased fertility was associated with collections of virgin females. Average weight +/- SD of the egg masses was 13.7 +/- 1.40 mg; the number of eggs per mass averaged 343. This method of obtaining egg masses from wild screwworm females is a cost-effective, sensitive alternative to the use of sentinel animals in the field. The use of rotted liver costs less, takes less time, and takes less equipment than the traditional sentinel animal technique.