Observations on the Mating Behaviour of the Crab Hole Mosquito Deinocerites cancer (Diptera: Culicidae)

Abstract

In Deinocerites, an aberrant offshoot of Culex, the larvae live in water in deep crab holes and the adults also are often found in the burrow. The males have elongate non-plumose antennae and specialized front claws, and often rest on the surface film. In observation cages the males associate with pupae (of either sex) at the surface of the water, hold them lightly with the claws and sense the pupal horns (spiracles) with their antennae. The male perceives the pupa at 1–2 cm. An emerging female elicits a strong response from males up to 15 cm. away; the males fight for possession and mating may be established before the female has fully emerged. The pupal skin continues to attract for several minutes thereafter. Emergence of the adult male was not successfully observed. Probably both pupal attendance and mating response depend on a chemical stimulus, which appears to be non-specific. The males also make slow exploratory flights near the cage walls, and a mating response may be elicited when their legs touch a resting insect. The response is made to either sex (perhaps more readily to the female) and again is non-specific. The two mating processes are presumably reinforcing, and both seem well adapted to the natural habitat provided the lack of specificity is tolerable. Several other mosquitoes, all of slow flight and restricted habitat, make similar irregular flights and mate on contact with resting females. Probably this behaviour represents the last phase of mating in more strongly flying (swarming) species, after the sexes are brought together by the auditory response mediated by the plumose antennae. In some mosquitoes the two patterns of behaviour coexist. Assembly at a swarm-marker and recognition in flight must be less necessary in non-dispersing forms in confined habitats, and most of all in Deinocerites. Several other crab hole mosquitoes show convergence or analogies with Deinocerites. The association with the pupa and the related attraction to the female at emergence find a parallel only in Opifex fuscus; but in Opifex these processes depend not on a chemical stimulus but mainly on vision, as befits an inhabitant of open sunlit pools.