Fine structure of antennal sensilla of the female sphinx moth, Manduca sexta (Lepidoptera: Sphingidae). II. Auriculate, coeloconic, and styliform complex sensilla

Abstract

The antennal flagellum of the female sphinx moth, Manduca sexta, bears eight types of sensilla: two trichoid, two basiconic, one auriculate, two coeloconic, and one styliform complex. We previously described the fine structure of the trichoid and basiconic sensilla (Shields and Hildebrand 1999). In this paper, we describe one type of auriculate, two types of coeloconic, and one type of styliform complex sensilla. The auriculate (ear- or spoon-shaped) sensillum is a small peg that averages 4 µm in length, is innervated by two bipolar sensory cells, and has structural features characteristic of an insect olfactory sensillum. Each of the two types of coeloconic sensilla is a small peg that averages 2 µm in length and is recessed in a cuticular pit. One type of coeloconic sensillum is innervated by five bipolar sensory cells and has structural features characteristic of an insect olfactory sensillum or olfactory-thermosensillum, while the other is innervated by three bipolar sensory cells and has structural features characteristic of an insect thermo-hygrosensillum. The styliform complex sensillum is a large peg that averages 38-40 µm in length and is formed by several contiguous sensilla, the number of which depends on the location of the peg on the flagellum. Each unit of the styliform complex sensillum is innervated by three bipolar sensory cells and has structural features characteristic of a thermo-hygrosensillum. We also ascertained the number and distribution of each of the eight types of sensilla on a single flagellomere (annulus) about midway along the flagellum of a female antenna. A total of 2216 sensilla were found on the dorsal, ventral, and leading surfaces of that annulus.