Geographic Variation in an Australian Species of Chaoborus (Diptera: Culicidae)

Abstract

Populations of an unnamed species of Chaoborus vary geographically in south-eastern Australia, along what appears to be a north-south cline. At least five characters are involved: in the adult, wing length and the colour of the style of the male coxite; in the larva, overall size, a complex character that includes relative breadth of the head, and degree of development of oesophageal molars. The dimensional characters of the larva were synthesized by means of principal component analysis; they show significant regressions on temperature. Latitudinal variation in size also occurs in the mosquitoes Anopheles annulipes and Culex vigilax, illustrating the occurrence in Culicidae of something analogous to 'Bergman's Rule' (of homoiotherms).