The formation of physogastry of the mushroom mite Dolichocybe perniciosa (Acari: Prostigmata: Dolichocybidae) has not been well understood. The shape and size of this mite vary dramatically. To evaluate the effects of environmental factors on the formation of physogastry we tested eight species of edible fungi hyphae, five temperatures and five humidity levels on the shape and size of physogastry. Dolichocybe perniciosa only fed on six species of edible fungi, Agaricus bisporus, Auricularia auricula-judae, Auricularia polytricha, Flammulina velutipes, Ganoderma lucidum and Lentinula edodes but failed to develop on the hyphae of Pleurotus geesteranus and Pleurotus eryngii. However, the six species of edible fungi had different effects on the formation and development of physogastry in D. perniciosa. The suitable temperature for the physogastric formation was from 18°C to 28°C at 75±5% RH, and the suitable humidity was from 22% to 92% at 25°C. The width of physogastries was less than 0.85 mm at five temperatures. The majority of physogastries were oblong or cylindrical under ideal temperature (25°C), but globular at a low temperature (13°C). The largest length and the highest length/width ratio were recorded at 25°C. The length and width of the physogastry were less than 4.0 mm and 0.8 mm, respectively, under tested humidity levels. The highest length/width ratio was 8.19 at 65% RH.