Environmental Influences and the Maxillary Index in Anopheles gambiae

Abstract

APPARENTLY contradictory reports of the behaviour of Anopheles gambiae in different parts of Africa have led to suggestions that more than one biological race of this species exists. In French West Africa, Holstein¹ has attempted to correlate these differences with variation in the maxillary index—the number of teeth on both maxillæ, divided by two. He has recognized a paucidentate population with a maxillary index of 13.5 and a multidentate population with an index of 15. The former is said to be anthropo-philic, mainly exophilic and to breed for preference in temporary pools in which the organic content of the water is low; the latter to be zoophilic, endophilic and to breed in permanent types of water of high organic content. Holstein has stated unequivocally that these two populations represent distinct biological races, and in this he has been supported by Campbell², working in Gambia, who was able to confirm the difference in maxillary counts in females emerging from different breeding sites.