Notes on the Simulium neavei Group of Simuliidae with particular Reference to S. nyasalandicum and S. woodi

Abstract

Simuliid larvae and pupae found in phoretic association with the fresh-water crab, Potamonautes niloticus (M.-Edw.) in Kenya rivers far from the haunts of Simulium neavei Roub. gave rise to adults which proved to be S. nyasalandicum De Meillon, a member of the neavei group. Very similar larvae, and pupae that exhibited minor differences from those of S. nyasalandicum, were found in the exhalant passages from the gill chamber of the crab. These yielded adults of S. woodi De Meillon, and no other species was found in this particular situation; nor were examples of S. woodi found on the external surface of the crab. As many as three larvae were found in one passage and, in another crab, a fully grown larva and pupa caused complete obstruction of the passage on one side. Apart from the security enjoyed by the larva in the sheltered position, it is thought probable that the association is essentially a commensal one.