RESPONSES OF MAXILLARY STYLOCONIC RECEPTORS TO STIMULATION BY SINIGRIN, SUCROSE AND INOSITOL IN 2 CRUCIFER-FEEDING, POLYPHAGOUS LEPIDOPTEROUS SPECIES

Chemosensory cells in the lateral and the medial styloconic sensillia on the galea of larval Mamestra configurata and Trichoplusia ni were investigated electrophysiologically. Sinigrin, sucrose, inositol and potassium chloride (KCl) were tested on both sensilla of each species. One of the four cells in both the lateral and medial sensilla of T. ni was sinigrin-sensitive, whereas in M, configurata, one cell in only the lateral sensillum was sinigrin-sensitive. The lateral sinigrin-sensitive cell of T. ni was eightfold more sensitive than the corresponding cell of M. configurata. One cell in the lateral sensillum of both species was sucrose-sensitive. The medial sensillum of M. configurata housed an inositol-sensitive cell but no cell sensitive to inositol was present in T. ni. One cell in the lateral and medial sensilla of both species was KCl-sensitive. Adaptation and dose-response data are given for the sinigrin-sensitive cells in both species. These are discussed in the context of deterrent-sensitive cells reported from other Lepidoptera. Comparative physiological and evolutionary aspects are considered and the general concepts of the lepidopteran deterrent cell is discussed.