SHORT COMMUNICATION HOW DOES A FLY CLING TO THE UNDER SURFACE OF

The climbing of flies on glass is a problem that still lacks an agreed solution. West (1862), who introduced the term 'tenent hairs ' for the trumpet-like structures on the pulvilli, regarded these as suckers which ensured adhesion by atmospheric pressure. But it is generally agreed that they are too small for that. Dahl (1885), studying adhesive organs in insects in general, favoured adhesion by 'Capillarattraction ' but he considered that other forms of cohesion and adhesion were operating as well. Rombouts (1884) opted for surface tension. In the most recent paper, Walker, Yule & Ratcliffe (1985) give a new description of the adhesive organs in the blowfly Calliphora, and conclude from calculations that surface tension of the lipid secretion under the tenent hairs provides an adequate adhesive force. The pad of setae at the lower extremity of the tibia of the first two pairs of legs, which is present in the adult of the blood-sucking bug Rhodnius and is used in climbing on a smooth surface (Gillett, 1932), has a totally different structure from that of the adhesive organ of the fly. In making a combined investigation (Gillett & Wigglesworth, 1932) we believed at first that surface tension in the lipid secretio