Adult ventral setal patterns in the family Phytoseiidae (Acari: Gamasina)

Abstract Fourteen pairs of setae and a single post-anal seta are known to occur on the ventral surface of the idiosoma of adult Phytoseiidae. Nine of these and the post-anal seta are present on all known species. Variations in the occurrence of the remaining 5 pairs produce a number of different ventral setal patterns which are examined in the present study. Because of extensive sexual dimorphism in the presence/absence of the variable setae, there are 9 basic ventral setal patterns for the adult females and 12 for the adult males. Variations in the points of insertion of the caudoventral setae produce 31 secondary patterns for females and 14 secondary patterns for males. Systems of notation for these setal patterns are proposed. Ventral chaetotaxy in the Phytoseiidae is compared to that of the Ascidae and the Otopheidomenidae.