Relationship between the olfactory sensilla of Papilio demoleus L. larvae and their orientation responses to different odours

Abstract

ABSTRACT Papilio demoleus larvae showed maximum attraction to odours of citral, cirtonellal and citronellol, slightly less to geraniol and 1‐limonene, and low attraction to hydroxy‐citronellal and geranyl acetate. These chemicals (except the last) are the main odorous constituents of the insect's host plant ( Citrus ) leaves. Phellandrene was almost inert, whereas farnesol and d‐limonene elicited a low, and linalool, eugenol and clove oil a high repulsion. Larvae deprived of one antenna and both maxillary palps were similar to normal larvae in their orientational responses. Normal larval responses changed with the inactivation of one or more of the three specific antennal sensilla. A full complement of the three sensilla was not essential for the normal larval response to certain chemicals. Any of the sensilla singly or in combination with any other sensillum could mediate the normal larval response (attraction) to citral and geraniol. For a few other chemicals, certain specific sensilla, singly or in a combination of two, mediated the normal response. Only for d‐limonene were all three sensilla essential for the normal response.