Distribution of color receptors in the larval eyes of four species of lepidoptera

Abstract

1. Caterpillars of the noctuid mothMamestra brassicae have six stemmata (I-VI) on either side of the head. Each stemma has seven photoreceptor cells (Fig. 1). Photoreceptor cells are spectrally differentiated into three types: UV, blue, and green (Fig. 2). 2. Stemmata I and III have five green and two blue receptors; stemmata II, V, and VI have four green, one blue, and two UV receptors; stemma IV has five green and two UV receptors (Table 1). 3. The spectral sensitivities of all photoreceptor cells inMamestra except for one, R4 of stemma IV, are the same as those of the anatomically equivalent cells inPapilio xuthus (Fig. 3). The R4 of IV in the former is a green receptor, while in the latter it is a blue receptor. 4. The fact that the R4s of stemma IV inMamestra andPapilio differ from each other physiologically may be related to the phylogenetic distance between the two species. Support for this point of view comes from the finding that inBombyx mori, thought to be relatively closely related toMamestra, the R4 in stemma IV is a green receptor (Fig. 6) while inPieris rapae crucivora more closely related toPapilio it seems to be a blue receptor (Table 2).