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 th eir food sources, mates, and oviposition sites. Insects offer certain advan tages as experimental models for the study of mechanisms of olfaction, and a thorough knowledge of the antennal olfactory sensory cells is essential f or 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 p resent the first thorough investigation of the structure, innervation, numb er, and distribution of sensilla on the antennal flagellum of female M. sex ta. The flagellum of the female moth bears eight morphological types of sen silla: two trichoid, two basiconic, one auriculate, two coeloconic, and one styliform complex. In this paper, we describe the two types of trichoid an d 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 b ipolar sensory cells, and the second type, a shorter hairlike sensillum ave raging 26 mu m in length, is innervated by either one or three bipolar sens ory cells. The first type of basiconic sensillum is a long peg, averaging 2 2 mu m in length, and the second is a shorter peg, averaging 15 mu m in len gth. Both types of basiconic sensilla are innervated by three bipolar senso ry cells. These trichoid and basiconic sensilla have structural features ch aracteristic of insect olfactory sensilla.