Responses of gravid screwworm flies,Cochliomyia hominivorax, to whole wounds, wound fluid, and a standard blood attractant in olfactometer tests.

Laboratory olfactometer bioassays were used to study attractiveness of whole animal wounds, wound fluid, and reconstituted dried blood to gravid screwworm flies,Cochliomyia hominivorax (Coquerel). Flies were attracted to odors from whole wounds that were infested with screwworm larvae but not to those from uninfested wounds that were 0-2 days old. A maximum of 59% of females were attracted to fluid from screwworminfested wounds, and the response changed little over fluid concentrations from 3.3 to 100%. However, blood tested over a similar concentration range yielded a significant linear relationship between log dose and response. Peak attraction was 82%. Attractancy of fluid collected from infested wounds declined when the fluid was stored at - 20 °C for more than four weeks but attractancy of a stored blood sample remained unchanged for three months. The blood attractant(s) was also heat stable and is suitable for use as a reference standard in bioassays.