Mixozercon Halašková, 1963

Díaz-Aguilar, Irma & Ujvári, Zsolt, 2010, New zerconid mites (Acari: Mesostigmata: Zerconidae) from Canada, with a review of the genus Mixozercon Halašková, 1963, Zootaxa 2555, pp. 1-29 : 2-3

Genus Mixozercon Halašková, 1963

Zercon (in part).― Sellnick, 1958: 337.

Type species: Parazercon sellnicki Schweizer, 1948: 23 , by original designation.

Diagnosis. Peritrematal shield bearing two setae: p1 short and smooth, p2 elongate and pilose; projecting beyond the lateral margin of idiosoma, situated in the anterior half of the shield. Small cuticular knobs present near p2. Peritrematal shield separated from podonotal shield by a narrow strip of interscutal membranous cuticle; in the female, shield truncate behind the fourth pair of coxae, in the male, its posterolateral end fused to ventri-anal shield. Peritremes short, straight or slightly bent. Adgenital sclerites absent, only a single pair of gland openings (gv2) present posterolateral to the genital shield. A pair of narrow post-genital sclerites may be present. Anterior margin of ventri-anal shield typically with two pairs of setae. Anterior ends of peritrematal shields fused together, and fused to the anterior margin of the dorsal shield to form a ventral extension of the vertex of the dorsal shield. Lateral margin of opisthonotum with 7–8 pairs of R-series setae. Dorsal cavities small and conspicuous. Epistome with a bifurcate medial process.

Remarks. Apart from the narrow separation of the peritrematal shield from the body margin and the absence of adgenital sclerites, Halašková (1963) mentioned the less conspicuous dentation of the margin of idiosoma as a differential character to separate Mixozercon from Zercon . She also drew attention to the different length and type of pilosity of the dorsal setae (as in the genus Prozercon Sellnick, 1943 ). However these differences are useless for distinguishing genera, because of the large interspecific variation within species of the same genus. As a result of the many intermediate character states combined in the single species, she gave the name Mixozercon to the newly established genus. Later the diagnosis of the genus was amended by inclusion of the posterior end of the peritrematal shield, which is generally truncate posteriorly, and the number of setae on the anterior margin of the ventri-anal shield ( Halašková 1969a; Błaszak 1974, 1979). But very little information can be found about the males of Mixozercon species. In our opinion, the other specific character of the genus, besides the setation, the marginal separation of the peritrematal shield, the shape of its posterior end, and the absence of adgenital sclerites, and the presence of setae Vl1, is the lateral fusion of the ventri-anal and peritrematal shields in males (however, this phenomena characterises other species of different Zerconidae genera as well).