Figure 1.

Main olfactory sensory organs of the silkmoth Bombyx mori. (A) A male silkmoth with its prominent antennae optimized for odorant detection. (B) Scanning electron micrograph of an antenna displaying the external morphology of sensilla trichodea. Scale bar: 25 μm. (C) Schematic diagram of an olfactory sensillum showing the detailed configuration of ORNs and accessory cells with respect to cuticular specializations. Three types of accessory cell surround the cell bodies of ORNs: tormogen (To), trichogen (Tr), and thecogen cells (Th). To and Tr cells secrete odorant-binding proteins into the sensillum lymph. Odorants are detected by ORs expressed on the dendritic membrane of ORNs. (modified from Jacquin-Joly and Merlin, 2004).