Chemically mediated host finding by Biosteres (Opius) longicaudatus, a parasitoid of tephritid fruit fly larvae

Host finding by the fruit fly parasitoid Biosteres (Opius)longicaudatus Ashmead was found to involve attraction to fermentation products emanating from rotting fruit, a probable site for location of host larvae. Bioassays conducted in the greenhouse with all saturated 1-, 2-, and 3-carbon primary alcohols, aldehydes, and organic acids indicated that acetaldehyde was the most active agent followed by ethanol and acetic acid. Rotting fruit was attractive irrespective of the presence of host larvae, and attraction was attributed to fungal fermentation products rather than to kairomones from host larvae.