Abstract
All, postembryonic instars of Hoploseius tenuis n. sp. are described and illustrated. This species is numerous in the pores of coniferous bracket fungi where it presumably feeds on the fungus. Discussed are: the relationship of this species to congeners, and the modification of the generic concept; the ontogeny of the body and leg setation, which includes larval, pustlarval and regressive deficiencies, and retardation; and the ontogeny of body elongation and its effect on the positions of setae. The adult morphology and setation of H. tenuis is briefly compared with that of an elongate digamasellid, Longoseius cuniculus Chant.

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