The Phytoseiidae have diverse habits. Some are apparently obligate predators, preying on other mites or on insects, others are facultative predators feeding on fungus hyphae, pollen, or plant sap when no prey is at hand (CHANT 1959a), and one species, Anthoseius hebetis DE LEON (1959b), is found only in the flowers of Heliotropium parviflorum where it probably feeds exclusively on pollen. Although phytoseiids are common in British Guyana there are no records of the occurrence of any species in that country. Through the kind invitation of Dr J. M. CHERRETT, a member of the University College of North Wales Guiana Expedition 1963 (OGDEN, 1964), I spent 13 days (22 Oct.—3 Nov. 1963) collecting mites in the Nature Reserve, near the Expedition’s Headquarters about 24 miles south of Bartica. The phytoseiids collected while with the Expedition and while in the Georgetown area are recorded below. The names of the plants from which mites were collected were provided, while with the Expedition, by Mr RUFUS BOYAN and Mr CHARLES SANDY, and while in the Georgetown area, by Mr R. PERSAUD and Mr DONALD DRAYTON.