The climbing organ of an insect, Rhodnius prolixus (Hemiptera; Reduviidœ)

Abstract

The climbing organ of Rhodnius prolixus is present in both sexes of the adult but absent in the nymphs. It occurs on the distal end of the tibia of the anterior and middle pairs of legs, and enables the insect to climb upwards on clean glass at almost a right angle, but it is of little use in going downward. The organ is a little oval sac of pliant chitin filled with blood bearing on its lower surface about 5000 tubular hairs 1[mu] in diameter, which appear to be the outlets of unicellular glands producing an oily secretion. At their free ends the anterior surface of these hairs is cut away obliquely so that only their hind margin comes in contact with the surface as the insect climbs. Among these hairs are about 50 delicate tapering hairs arising from large sockets and projecting slightly beyond the others. These appear to be sense organs. They are surmounted by a spindle-shaped mass of cells giving off a nerve fibre. A model of the climbing organ was made consisting of a disc separated from a glass plate by a wedge of oil. This can be moved readily in one direction (towards the open end of the wedge), but is very resistant to movement towards the point of the wedge. Evidence is brought forward that this is due to adhesion or seizure caused by the breaking down of the oil film at the point of the wedge.