The behavior and biology of the aphidophagous hoverfly Pseudodorus clavatus (F.) were studied in the laboratory. The survival of P. clavatus larvae fed Aphis spiraecola Patch was 24% from egg to adult, not significantly different from larvae fed Toxoptera citricida (Kirkaldy) (36%). However, larval development was significantly faster on the T. citricida diet and the resulting adults were 50% heavier. Cannibalism of eggs and larvae was common among newly eclosed larvae independent of the presence of aphids, but not among older larvae. The adult sex ratio at eclosion was 0.485 (♀:♂) but 50% of females died before oviposition. Male flies lived for a mean of 16.8 ± 3.8 d and ovipositing females for 29.8 ± 1.9 d at 23°C. The prereproductive period for females averaged 6 d, and the majority of eggs were laid during morning hours, oviposition peaking between 0830 and 1030 hours. There was no preference among naïve females to oviposit near either aphid species and eggs were also laid on aphid-infested terminals containing conspecific eggs or larvae. Oviposition was elicited on plant tissues with aphids or residues of aphid honeydew but not on clean plant tissues. Samples of P. clavatus larvae collected from Aphis spiraecola on Viburnum spp. in winter in central Florida were heavily parasitized by the solitary parasitoid Eurydinotelloides bacchadis (Burks) (Hymenoptera: Pteromalidae).