Receptor neurones in three heliothine moths responding to floral nd inducible plant volatiles

Summary. Some plant volatiles are produced in response toherbivory of several insect species, including heliothinelarvae. In the present study of female heliothine moths, fourco-located receptor neurone types were identified, of whichthree types responded strongest to the inducible compoundsE--ocimene, E,E--farnesene and E,E-TMTT, respectively.The fourth type responded strongest to geraniol,which is a common floral volatile. The narrow tuning ofeach receptor neurone type was demonstrated by responsesto a few structurally-related monoterpenes, sesquiterpenes,homo-terpenes and monoterpene alcohols, respectively, outof hundreds of plant constituents tested. The four neuronetypes showed the same relation of spike amplitudes andranking of effective compounds in the three heliothinespecies; the polyphagous Heliothis virescens andHelicoverpa armigera and the oligophagous Helicoverpaassulta. The results indicate the presence of functionallysimilar types of plant odour-receptor neurones in the threerelated species, and suggest conservation or reappearance offunctionally similar olfactory receptors in related species,independent of the evolution of polyphagy and oligophagy.