The Australian Chaoboridae (Diptera)

Abstract

Australia has a small but very interesting fauna of Chaoboridae, with some nine species in four genera. Chaoborus has five species, four of them new; three, perhaps four, are most closely related to species in Asia and Africa, but one (C. vagus, sp. nov.) seems related to the more 'primitive' subgenera of the Holarctic Region. The endemic Prornochlonyx and Australomochlonyx have one species each. Corethrella has at least two, one mainly southern and taxonomically distinctive, the other found in the vicinity of Darwin and very similar, even identical, to C. urumense Miyagi, of the Ryuku Is. The relationships of other Corethrella from Queensland remain unclear. Doubt also remains about the status of 'forms' of Promochlonyx, from Queensland, Victoria, and Western Australia. All species and 'forms' are described or redescribed, together with notes on their biology, distribution, and relationships.

Numerical methods are employed to examine relationships within Promochlonyx and Corethrella, and between all genera in the family. A judicious mixture of phenetics and cladistics confirms that the Chaoborinae (i.e. excluding Corethrella and Eucorethra) form a credibly monophyletic group, and suggests that Corethrella is perhaps an early offshoot of the culicid stock; that Eucorethra represents a very primitive stock arising from near the root of the Culicoidea; and that Promochlonyx and Australomochlonyx arose separately or via a shared ancestor early in the history of the Chaoborinae. There is clear evidence that the family dates back to (at least) the early Cretaceous, and it seems overwhelmingly credible that Promochlonyx and Australomochlonyx, and possibly also C. vagus, are relicts from the Gondwanaland fauna or descended from such a relict.