The biology of Galendromus helveolus (Chant) (Acari: Phytoseiidae) was, studied using Eotetranychus sexmaculatus (Riley) (Acari: Tetranychidae) as the food source. Larvae developed to protonymphs without feeding. The total developmental times of G. helveolus were 12.36, 9.66, 5.63, 4.61, and 4.84 d at 18, 20, 25, 30, and 32°C, respectively, at 76% RH. A higher percentage of eggs (32%) did not hatch and higher larval mortality (37%) occurred at 32°C. The intrinsic rates of natural increase (rm) at 16, 20, 25, 30, and 32°C were 0.100, 0.153, 0.286, 0.327, and 0.144, respectively. The optimal temperature range for G. helveolus was considered to be between 25 and 3O°C. The sex ratio of G. helveolus was strongly female biased (females/total = 0.82). G. helveolus was able to survive and reproduce on Panonychus citri (McGregor), Eutetranychus banksi (McGregor), and Tetranychus urticae Koch (Acari: Tetranychidae) with a daily rate of oviposition of 2.21, 1.96, and 2.25, respectively, compared with 2.37 when fed only Eotetranychus sexmaculatus. Females of G. helveolus were observed to feed and survive for 10 d on Phyllocoptruta oleivora (Ashmead) (Acari: Eriophyidae), but no eggs were laid. In addition, G. helvelous protonymphs and deutonymphs were observed feeding on P. oleivora. A low percentage of the predator eggs (8%)was able to develop to the adult stage on P. oleivora compared with 82% when provided Eotetranychus sexmaculatus and 70–80% when provided Panonychus citri, Eutetranychus banksi, or T. urticae.