The slit sense organs (SSOs) of spiders are mechanoreceptors measuring strains in the cuticle (Barth, 1978). They were discovered by Bertkau (1878) and studied quite intensively by many authors in the following decades (review in Barth, 1967). They are stimulated by a compression perpendicular to the long axis of the slit (Barth, 1972a,b, 1973). The fine structure of slit sensilla is well known...