Type species: Stigmaeus loadmani Wood, 1967: 102; based on adult females.

Description of adults (Figs. 1­17). Idiosoma oval in dorsoventral view. Chelicerae separate. Palp robust; tibial claw slightly shorter than palptarsus; accessory claw slender. Terminal palptarsal eupathidia fused basally at insertion point and distally divided into 3 minute prongs. Fundamental setation from palptrochanter to palptarsus on adult: 0, 3, 1, 2 + 1 claw + 1 accessary claw, 4 + 1 1 subterminal spine­like eupathidium + 3 basally fused eupathidia. Subcapitulum with 2 pairs of setae (m and n), both posterolaterad of pharynx, m­m wider than n­n. Propodosoma covered with a large triangular shield, which bears 1 pair of eyes and 4 pairs of setae (vi, ve, sci, sce), sci mediad of sce; postocular body absent. Central hysterosomal shield well sclerotized, bearing 3 pairs of setae (c 1, d 1, e 1). Setae c 2, d 2, e 2 and f 1 situated on small platelets. Suranal shield (H) integral, bearing 2 pairs of setae (h 1 and h 2). Endopodal shields present around coxae I and II, but absent around III and IV. Ventral setae 3 pairs (1 a, 3 a and 4 a). Aggenital setae 3 pairs (ag 1, ag 2 and ag 3). Genital and anal openings contiguous, with 1 pair of genital setae (g 1) and 3 pairs of pseudanal setae (ps 3 , ps 2 and ps 1) on adult female. Leg tarsal claws well developed, without a prominent membranous arolium. Empodium rod­like, bearing 3 Y­shaped tenent hairs. Fundamental setation of legs I­IV on adult female: coxae 2, 1, 2, 2; trochanters 1, 1, 1, 0; femora 5, 4, 3, 2; genua 3 + 1, 2, 0, 0; tibiae 5 + 1 p, 5 + 1 p, 5 + 1 p, 5 + 1 p; tarsi 13 + 1, 9 + 1, 7 + 1, 7 + 1.

Etymology. The generic name Primagistemus is combined from the Latin prefix “ primi ” (primal) and the generic name, Agistemus. It is masculine in gender.

Taxonomic position. Mites of the genus Primagistemus have 4 pairs of setae on the propodosomal shield, like those in some genera (e.g. Stigmaeus, Pseudostigmaeus, Summersiella, Eustigmaeus and Cheylostigmaeus). However, many other characteristics (e.g., both subcapitular setae m and n posterolaterad to pharynx; palpgenu with only 1 seta on the adult, terminal eupathidia on palptarsus mostly fused, coxa II with only 1 seta; endopodal shields around coxae III­IV absent, trochanter III with 1 seta) indicate that Primagistemus is much more closely related to the genera, Agistemus, Zetzellia, Neilstigmaeus, Pilonychiopus and Parastigmaeus.

Remarks. Adult females of Primagistemus gen. nov. are distinguished from those of Agistemus by having 4 pairs of setae on the propodosomal shield, by lacking postocular bodies, by having 3 pairs of aggenital setae, and by having 2 setae on genu II. They are also distinguished from those of Stigmaeus by the terminal eupathidia on palptarsus being mostly fused and subterminally separated into 3 minute prongs, by both subcapitular setae posterolaterad of pharynx, by having only 1 seta on coxa II, and by lacking endopodal shields around coxae III­IV.