This paper deals with the detailed morphological observation of larva, protonymph and deutonymph, as well as female and male adults of Neoseiulus californicus (McGregor) based on laboratory reared specimens. The main changes are as follows: larva with one dorsal shield, while protonymph with two, which fused into a holodorsal shield in deutonymph; 9 pairs of dorsal setae in larvae, 14 pairs in protonymph, and 19 pairs in deutonymph and adult; the immature stages without discernible ventrianal shield, though hypoplastic shield, a weakly sclerotized small plate around the anal pore, present in the protonymph and deutonymph. larva and protonymph each with seven pairs of ventral setae, while deutonymph and adult each with 12 pairs; movable digit with one or two teeth in larva, three teeth in protonymph, deutonymph or adult. The development of morphological traits in ontogenesis of N. californicus could provide helpful basis to identify it practically from its relatives.
Keywords: Acari, Morphological ontogeny, immature stages, identification, predator mite.