A large number of male and female tenerals and young non-teneral female G. pallidipes were attracted to the exterior of the trap but appeared not to enter the trap readily. About 20% of tenerals of both sexes that visited the trap were captured in the retaining cage and the remaining 80% on the outside. The sex ratio of flies stuck on the outside was 1:1 whereas that of flies from the retaining cage was 1:1.5 females:males. The efficiency of the trap for non-teneral G. pallidipes was about 39%. Direct observation using binoculars from a stationary vehicle about 10–15 m from the trap showed that the catching efficiency of the biconical trap was 30% for a total of the four categories of non-teneral females and males, and teneral females and males.
