Volatiles from Waste Larval Rearing Media Attract Gravid Screwworm Flies (Diptera: Calliphoridae) to Oviposit

Gravid screwworm sies, Cochliomyia hominivorax (Coquerel), are attracted to the volatiles from waste larval rearing media to deposit eggs. Studies were conducted to identify volatile chemicals from the waste larval media and determine their effectiveness to attract gravid sies to oviposit. Volatiles were collected using solid-phase microextraction method, and Þve active chemicals, namely, dimethyl disulÞde, dimethyl trisulÞde, phenol, p-cresol, and indole, were identiÞed using gas chromatographyÐmass spectrometry. In electroantennography studies, antennae of gravid screwworm sies, Cochliomyia macellaria (F.), responded positively to each of the identiÞed compounds. A synthetic blend of these Þve compounds in the ratio of 335:200:57:1:12 was prepared and tested for its effectiveness to attract both C. hominivorax and C. macellaria using laboratory bioassay methods. SigniÞcantly more gravidC. macellaria were attracted to and landed on substrates treated with 10-fold diluted blends compared with those landed on substrates treated with ethanol only (as control). Only a few young females and young and old males were attracted to the substrates treated with the synthetic blend. The C. hominivorax females laid signiÞcantly more eggs on substrates treated with waste media, 10-fold diluted blend, and 100-fold diluted blend than on substrates with undiluted blend or ethanol. Similarly, C. macellaria deposited signiÞcantly more eggs on substrates treated with waste media, 10-fold diluted blend, and 100-fold diluted blend compared with substrates with undiluted blend or ethanol. C. macellaria females deposited signiÞcantly less amount of eggs than did C. hominivorax females. These results indicate that the synthetic blend of Þve compounds identiÞed may serve as an oviposition attractant for C. hominivorax as well as for C. macellaria.