Riscus, Den Heyer, 2006

Heyer, Jacob Den & Castro, Tatiane Marie Martins Gomes De, 2012, New Neotropical cunaxine species (Acari: Prostigmata: Cunaxidae), Zootaxa 3265, pp. 22-42 : 36

Genus RISCUS Den Heyer, 2006

Riscus Den Heyer, 2006: 195 –201

Type species Riscus thailandensis Den Heyer, 2006

Genus description. With the acquisition of material from South America the genus characteristics, provided by Den Heyer (2006), have to be revised. They are: very poorly sclerotised, soft-bodied mites; no plates. Setae sci, being the longest idiosomal st-seta and almost reaching the nearest sensillum vi, occur anteriad to a line between sensillae sce. Sensillae are finely and densely pilose. Setae f2 absent. Lyrifissures im laterad to imaginary line e1- f1. Setae hg4 occur almost in line with hg3 forming a transverse row. Hysterogastral setae 3 or 4 pairs. Genital papillae 2 or 3 pairs and small. Genital valves with 4 or 5 pairs of g-setae in female, 4 in tritonymph and 3 in the deutonymph. One pair of paragenital setae flank the genital valves. Paracoxal setae (pcs) on edge of coxae IV or on integument. No para-anal setae. Lyrifissures ih close to anus. The hypognathum possesses a pair of peg-like structures (proprioceptors) laterally to the base of the chelicerae. Palpal genu with 3 or 4 setal structures which may be straight or curved. Palptibiotarsus with a tubercle of varying stoutness. Solenidion formula (all types, i.e. asl, bsl, dtsl, tsl) for genua I-IV: 5 or 4 – 2 – 1 – 1; tibiae I-IV: 2 – 1 – 1 - 0; tarsi I-IV: 7 – 3 – 1 - 0. Femora I and II not divided, III and IV clearly divided. Tarsal lobes very small. Sts- formula for basifemora 3 – 3 – 2 – 1 sts, telofemora 4 – 4 – 4 – 4 sts. All legs are shorter than the body with legs IV being the longer. The known representatives of this genus inhabit an array of plants. Riscus thailandensis occur on Mangifera indica L.; R. austroamericanus sp. nov. was found on Coffea arabica L., Solanum nigrum L., Euterpe sp. and Pisidium guajava . No information exists on their colour and boilogy.