The accumulation of late-instar larvae of the predator,Toxorhynchites rutilus rutilus(Coquillett), during late summer and early fall in automobile tires on an island near the west coast of Florida reduced the average densities of prey larvae ofAedes aegypti(L.), from more than 100 to less than 5/tire. Then during the winter months, while the predators overwintered as diapausing last-instar larvae, the number of tires positive for prey increased from 13 to 43%. With the termination of diapause in the spring, the predator population again increased, and the prey population decreased. The findings are discussed in the context of usingToxorhynchitesTheobald as a biological control agent against container breeding mosquitoes.