Fine structure of antennal sensilla of the female sphinx moth, Manduca sexta (Lepidoptera: Sphingidae).: I.: Trichoid and basiconic sensilla

Olfaction is the principal sensory modality through which insects locate their food sources, mates, and oviposition sites. Insects offer certain advantages as experimental models for the study of mechanisms of olfaction, and a thorough knowledge of the antennal olfactory sensory cells is essential for such studies. While the sphinx moth, Manduca sexta, has proved to be an especially favorable experimental model in studies of pheromone processing in males, little is known about the female olfactory system, including the antennal olfactory sensilla. In this and another paper in this series, we present the first thorough investigation of the structure, innervation, number, and distribution of sensilla on the antennal flagellum of female M. sexta. The flagellum of the female moth bears eight morphological types of sensilla: two trichoid, two basiconic, one auriculate, two coeloconic, and one styliform complex. In this paper, we describe the two types of trichoid and two types of basiconic sensilla. The first type of trichoid sensillum, a long hairlike sensillum averaging 34 mu m in length, is innervated by two bipolar sensory cells, and the second type, a shorter hairlike sensillum averaging 26 mu m in length, is innervated by either one or three bipolar sensory cells. The first type of basiconic sensillum is a long peg, averaging 22 mu m in length, and the second is a shorter peg, averaging 15 mu m in length. Both types of basiconic sensilla are innervated by three bipolar sensory cells. These trichoid and basiconic sensilla have structural features characteristic of insect olfactory sensilla.