The morphological ontogeny of Peloribates longipilosus Csiszár, 1962, in Csiszár & Jeleva, 1962 is described and illustrated. The juveniles of this species have most prodorsal and gastronotal setae long and some gastronotal setae with excentrosclerites. The larva has 12 pairs of gastronotal setae, including h₃, whereas the nymphs have 15 pairs. The larva has excentrosclerites at one pair of setae (c₂), whereas nymphs have them at 11 pairs (c₁ c₂, d-l- and h-series). The notogaster of adult loses seta c₃ and 14 pairs of long setae remain, and this setal pattern is the most primitive in Haplozetidae, other species have 10, 11 or 13 pairs of notogastral setae.