Oviposition habitat selection by the mosquito Culiseta longiareolata in response to risk of predation and conspecific larval density

1. Most female Culiseta longiareolata (Diptera: Culicidae) avoid ovipositing in pools that contain the predatory backswimmer Notonecta maculata. Such oviposition habitat selection has been suggested to reflect a trade-off between the risk of predation on larvae and potential density-dependent fitness costs. This putative trade-off was examined. In particular, evidence was sought in support of direct female response to local heterogeneity in habitat quality. 2. Three habitat types were established using artificial outdoor pools: predator pools, and non-predator pools with either low or high densities of Culiseta larvae. During each experimental night, females were offered one of the three possible pair-wise treatment combinations. 3. The majority (≈88%) of females oviposited in low-density pools rather than in the predator- or high-density pools. Furthermore, a substantially higher proportion of females oviposited in predator pools when faced with the high-density alternative, however this was due largely to fewer females ovipositing in high- vs low-density pools. 4. Females of a second mosquito species (Culex laticinctus), the larvae of which are at a lower risk of predation, were predicted to exhibit weaker aversion to N. maculata; this prediction was supported only weakly. 5. Oviposition habitat selection by female C. longiareolata does not appear to involve a behavioural response that is based on individual assessment of local heterogeneity in relative pool quality, at least not at the spatial scale examined here; alternative explanations are discussed.