The biology ofGalendromus helveolus(Chant) (Acari: Phytoseiidae) was, studied usingEotetranychus sexmaculatus(Riley) (Acari: Tetranychidae) as the food source. Larvae developed to protonymphs without feeding. The total developmental times ofG. helveoluswere 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 forG. helveoluswas considered to be between 25 and 3O°C. The sex ratio ofG. helveoluswas strongly female biased (females/total = 0.82).G. helveoluswas able to survive and reproduce onPanonychus citri(McGregor),Eutetranychus banksi(McGregor), andTetranychus urticaeKoch (Acari: Tetranychidae) with a daily rate of oviposition of 2.21, 1.96, and 2.25, respectively, compared with 2.37 when fed onlyEotetranychus sexmaculatus. Females ofG. helveoluswere observed to feed and survive for 10 d onPhyllocoptruta oleivora(Ashmead) (Acari: Eriophyidae), but no eggs were laid. In addition,G. helvelousprotonymphs and deutonymphs were observed feeding onP. oleivora. A low percentage of the predator eggs (8%)was able to develop to the adult stage onP. oleivoracompared with 82% when providedEotetranychus sexmaculatusand 70–80% when providedPanonychus citri, Eutetranychus banksi, orT. urticae.