Field comparisons of attractants for the screwworm fly (Diptera: Calliphoridae) in a tropical dry forest in Costa Rica.

Field trials were conducted to determine the best attractant for adults of the screwworm, Cochliomyia hominivorax (Coquerel), in Costa Rica. The five attractants were wounded sentinel sheep, decayed fruit, rotted beef liver, rotted fish, and medium used to rear larvae of this blow fly. Significantly more adults came to rotted liver than any other attractant. No adults were captured in traps baited with rotted fruit. Significantly more males came to beef liver than were captured at other baits; males were rarely encountered at wounds. Ovarian development of females obtained with different attractants indicated that proportionally more gravid females visited wounded animals than were caught in traps with proteinaceous baits. Most females had mated by egg stage five and mating and and parity in the populations that visited different attractants were similar. Significantly more females (81%) marked initially at wounds returned to wounds than visited traps baited with liver or fish.