Mediostigmaeus, Fan, Qing-Hai & Walter, David E., 2005

Fan, Qing-Hai & Walter, David E., 2005, Mediostigmaeus gen. n. (Acari: Stigmaeidae), with the description of a new species from the USA, Zootaxa 1036, pp. 21-29 : 22-23

Genus Mediostigmaeus gen. n.

Type species: Eryngiopus citri Rakha & McCoy, 1984 ; by present designation.

Diagnosis

Adult female. Idiosoma broadly oval in dorsoventral view, generally red or orange in life. Chelicerae separate. Palptibial claw subequal to or slightly shorter than palptarsus; accessory claw slender, seta­like; terminal eupathidia on palptarsus mostly fused and split into 2–3 vestigial prongs; counts of setae and solenidia from palptrochanter to palptarsus: 0, 2, 1, 2+1 claw + 1 accessary claw, 4+1 +1 subterminal spiniform eupathidium + 3 eupathidia (mostly fused). Subcapitulum with 1 pair of setae posterolaterad of pharynx. Prodorsum mainly striated, prodorsal shield reduced, bearing 2–3 pairs of setae, sce present, on platelets; eyes present, pob present but indistinct. Dorsal hysterosomal area C– F mainly striated, with a weakly sclerotized central shield and one pair of minute platelets anteromediad of d1; setae d1 and d2 each situated on a tiny platelet; humeral shields minute or vestigial, dorsolateral, bearing setae c2; intercalary shields (F) divided along midline, each with a seta (f1). Suranal shield (H) entire, with 2 pairs of setae (h1 and h2), h3 absent. Coxisternal shields I–II and III–IV absent. Ventral opisthosoma with 3 pairs of aggenital setae; genito­anal valves with one pair of genital setae and 3 pairs of pseudanal setae. Leg tarsal claws robust; empodial shafts branching into tenent hairs before extending beyond tips of claws, with 3 pairs of tenent hairs; counts of setae and solenidia on legs I–IV: coxae (excluding 1a, 3a and 4a) 2 + 1 elcp, 1, 2, 1; trochanters 1, 1, 1, 1; femora 4, 4, 2, 2; genua 1+1, 0, 0, 0; tibiae 5+1 p, 5+1 p, 5+1 p, 5+1 p; tarsi 8+1, 7–8+1, 6+1, 6.

Adult male. As in adult female but without genital setae; with an aedeagus; tarsi I–II each with two solenidia.

Deutonymph. Idiosoma and legs as in adult female but without genital folds and setae.

Protonymph. Ventral setae 4a and genital setae absent; with one pair of aggenital setae; with fewer setae on segments of legs.

Larva. Without subcapitular setae, ventral setae 4a, aggenital setae and leg IV.

Etymology

The genus name, Mediostigmaeus , is a combination of the prefix medio (middle) referring to the position of internal pair of scapular setae, with the genus name Stigmaeus .

Remarks

Members of the new genus are similar to those of Mediolata in having only one pair of subcapitular setae which readily separates them from other known genera of Stigmaeidae . This genus can be easily distinguished from Mediolata by the palptibial claw being subequal to palptarsus, and setae c1, d1, d2, e1, e2, and f1 situated on individual platelets. It also resembles the genus Eryngiopus in the patterns of dorsal idiosoma and genito­anal area, but can be separated from the latter by having weakly sclerotized central hysterosomal shield, one pair of subcapitular setae and lacking coxisternal shields. This is an intermediate genus between Mediolata and Eryngiopus .

The following couplets indicate distinguishing characters of the known genera of Stigmaeidae (adults).

1. With 1 pair of subcapitular setae .................................................................................. 2

­ With 2 pairs of subcapitular setae ........... Other 27 known genera ( Fan & Zhang 2005)

2. Palptibial claw prominent, subequal to palptarsus; hysterosomal setae c1, d1, d2, e1, e2, and f1 each on an individual platelet ......................................... Mediostigmaeus gen. n.

­ Palptibial claw small, no more than 1/2 length of palptarsus; at least two of setae c1, d1, d2, e1, e2, and f1 sharing a shield ............................................. Mediolata Canestrini

The following couplet indicates distinguishing characters of species of Mediostigmaeus gen. n. (adults).

1. Tarsus II with 7+1; setae sci nearly reaching bases of sce; central hysterosomal shield extending posteriorly to bases of e1............ M. citri (Rakha & McCoy) comb. n.

­ Tarsus II with 8+1 ( Fig. 3 B); sci about 1/2 distance between sci and sce; central hysterosomal shield not extending to bases of e1 ................................. M. floridanus sp. n.

Figures

FIGURE 3. Mediostigmaeus floridanus sp. n. (adult female). A, leg I; B, leg II; C, leg III; D, leg IV; E, pretarsus II.