Fine structure and neurophysiology of a gustatory sensillum on the ovipositors of Metasyrphus venablesi and Eupeodes volucris (Diptera: Syrphidae)

A typical uniporous contact chemosensillum was identified on the ovipositor of two aphidophagous syrphids, Metasyrphus venablesi (Cn.) and Eupeodes volucris O.S. (Diptera: Syrphidae). Fine structural study of the sensillum of M. venablesi revealed one mechanosensitive and five chemosensitive neurons. Single sensillum recordings from both species showed ovipositor sensititivy to various compounds characteristic of the oviposition site including aphid honeydew, sucrose, the amino acids alanine and tryptophan, an oxidation product of tyrptophan (indoleacetaldehyde), and water.