Mideopsidae Koenike, 1910

Pešić, Vladimir, Cook, David, Gerecke, Reinhard & Smit, Harry, 2013, The water mite family Mideopsidae (Acari: Hydrachnidia): a contribution to the diversity in the Afrotropical region and taxonomic changes above species level, Zootaxa 3720 (1), pp. 1-75 : 5

Family Mideopsidae Koenike, 1910

Mideopsellinae Lundblad, 1937, syn. nov.

Phreatomideopsinae Schwoerbel, 1986, syn. nov.

Diagnosis: Idiosoma flattened; dorsal and ventral shields present. Dorsal and ventral shields usually separated but rarely fused anteriorly. Surface of dorsal shield varying from smooth to some development of sculpturing or often ridges. Lateral eyes lying below integument. In general, Cx-IV triangular in shape with medial margins reduce to medial angles but in occasional cases with moderately developed medial margins. Generally Cxgl-2 (and in one genus a second pair of glandularia) lying immediately posterior to Cx-IV, but occasionally Cxgl-2 lateral to genital field. Projections (either extensions of Cx-IV or condyles associated with openings for insertion of IV-L) variously developed or actually absent. Genital field completely surrounded by ventral shield in both sexes. Genital field with a membranous gonopore which is narrow in males but varying from slightly to much wider in females. Three (the typical number) to seven pairs of Ac located in a row on each side. Females with Ac flanked laterally by setaebearing sclerites which may be separate but are most often fused with ventral shield. Gnathosoma not fused with ventral shield and chelicera not fused medially. Palp 5-segmented with P-4/5 occasionally uncate (i.e., distal end of P-4 much higher than the dorsally inserted proximal end of P-5) but more commonly not, and with varying degrees intermediacy between the two extremes. Legs with or without swimming setae. Sexual dimorphism generally involves only the genital field, but the idiosoma, legs and palp occasionally exhibit varying degrees of sexual dimorphism.

Remarks: The morphology of the larva, not here diagnosed, indicates the family belongs in the superfamily Arrenuroidea.

Discussion: The subfamily Mideopsellinae was based almost exclusively on the possession of uncate palps. The relationship of Mideopsella with its uncate palp to other South American species lacking an uncate palp, but with a large ventral tubercle on P-4 is evident. However, the other two genera with uncate palps are very distinct from each other, both in idiosoma morphology and well as structure of the palps. All three of these genera ( Mideopsella , Mideopsellides and Tiramideopsis ) are very distantly related to each other and, with the exception of Mideopsella , possible ancestors from which the uncate palp may have evolved are unknown. Without question the concept of the subfamily Mideopsellinae is extremely artificial and we have placed it in synonymy with Mideopsidae . Although some of the included genera are more closely related to each other, we are treating them in the generic diagnoses as equivalent genera.

As results from our redescription of Phreatomideopsis arrenuripalpis (see below), Schwoerbel’s (1986) statement that the palp of this taxon should be described “as in typical Arrenurus ” is not correct. In general shape and setation, the P-4 fits well the diagnosis of Mideopsidae and does not justify the estabishment of a proper subfamily. As also all other character states given in the diagnosis of Phreatomideopsinae Schwoerbel, 1986 are not distinctive, we synonymize here with Mideopsidae . One of the difficulties faced in doing this revision is the poor knowledge of the South American fauna. Although many species of Mideopsidae have been described from this area most are inadequately diagnosed and illustrated. Also, a majority of the species are known only from the female and it is usually the male which best demonstrates generic characteristics. This has been a special problem for the South American Mideopsides , Neoxystonotus and a special species group assigned to the old subgenus Mideopsis . This latter species group differs from the Holarctic members of the old subgenus in a number of characteristics. We debated whether to place these latter South American species in a separate genus but decided, because of the inadequate description of these mites and the fact that males were known for so few species, to consider them a special species group in the genus Mideopsis . However, in the diagnosis of the genus Mideopsis below, characters of this South American species group that differ from those of the Holarctic species will be placed in parentheses.