Fig. 1.

Scanning electron micrograph of different types of olfactory sensilla on the distal margin of a ring-shaped segment in the middle part of the cockroach antenna. The single-walled type C (swC) sensillum houses the ON and OFF ORNs. The basal surface of the slightly curved hair is grooved; distally, the surface is smooth and perforated by pores. The shorter single-walled type B (swB) sensillum contains four ORNs. The hair is bent and ends bluntly; the wall possesses pores. The double-walled type A and B (dwA and dwB) sensilla have finely longitudinal grooves into which pore open. Both dw-types are associated with four ORNs