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We present an analysis of the functional response of the predator Toxorhynchites rutilus rutilus (Coquillett) to changes in the density of the larvae of Aedes aegypti (L.) (Diptera: Culicidae). The experiment was replicated for five different ages, and at three different densities of the predator. The data were fitted to Rogers' (1972) random predator equation by non-linear least-squares in order to estimate searching efficiency and handling time for each experimental treatment. The data show that estimated searching efficiencies are highest at intermediate ages of the predator for all predator densities tested. Handling time declines exponentially with increasing predator age. There is a marked interference effect; searching efficiency decreases with increased predator density, and this is most pronounced at intermediate prey ages. Estimated handling times increase with predator density at a rate which declines with increasing predator age.

1. Oviposition of the mosquito Toxorhynchites moctezuma Dyar & Knab was investigated in four types of tropical forest in Trinidad, West Indies, using surrogate and natural ovitraps. Larvae of Tx. moctezuma are obligate predators that might be useful for the biological control of Aedes aegypti (L). 2. Significantly more oviposition occurred in seasonal-deciduous forest than in either montane or evergreen-seasonal forest. 3. Oviposition in surrogate containers (black-painted polystyrene cups, 90 mm diameter) was compared with that occurring in typical natural containers (nutpots of Lecythis zapucajo Aublet). Surrogate ovipots were relatively insensitive indicators of oviposition activity, and would be an inefficient means of harvesting Tx. moctezuma eggs. 4. Implications for the collection, culture and mass release of Tx. moctezuma are discussed.

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