Accumulation ofDendrobium superbum (orchidaceae) fragrance in the rectal glands by males of the melon fly,Dacus cucurbitae

4-(4-Hydroxyphenyl)-2-butanone was characterized from flowers of the orchidDendrobium superbum as a specific attractant factor for the male melon fly,Dacus cucurbitae. The male flies compulsively licked the flower surface and sequestered the compound in significant quantities in their rectal glands. The compound was detected within 6 hr after ingestion and was retained for more than six days in the rectal gland sacs.