Callosobruchus maculatus(F.), the cowpea weevil, previously known to prefer smooth over rough seeds, readily distinguishes between rough and smooth varieties of cowpeas,Vigna sinensisL. The Hopkins' host-selection principle does not apply to weevils ovipositing on cowpeas. The surface of the underlying cotyledons is the same texture in both rough and smooth seeds and the seed coat is not a reprint or replicate of this surface. More 1st instar larvae successfully penetrate the seed coat in smooth than in rough seeds. The arrangement of macrosclereids of the epidermal layer of seed coats and how eggs are attached to the seed surface account for differences in larval penetration of rough- and smooth-coated varieties.