Environmental Factors affecting Hairiness in Mosquito Larvæ

Abstract

Rosen and Rozeboom¹ have described a wide range of variation in larval hairiness in the Aedes scutellaris group of mosquitoes in Polynesia, and have shown that hairiness is conditioned by some environmental factor common in, but not restricted to, tree-holes. A similar situation has now been discovered in the related Aedes albopictus in Singapore; here, larvæ from tree-holes frequently have many of the body hairs longer, stouter and with more branches than in the normal form (Fig. 1). A colony established from hairy larvæ produced only normal larvæ in the laboratory, and the hairiness is clearly produced by some environmental factor. Rearing experiments showed that larvæ raised in the contents of some, but not all, tree-holes became hairy; siblings from the same batch of eggs, reared in tap water plus yeast, or in grass infusion, were normal. The related Aedes aegypti also gave hairy larvæ when reared in the appropriate medium, but Culex fatigans larvæ were not affected.