A NEW GENUS AND A NEW SPECIES OF MICROT-ROMBIDIINAE THOR, 1935 (ACARI: TROMBIDIIDAE)
ZHANG ZHI-QIANG XIN JIE-LIU(Department of Biology, Fudan University, Shanghai)
Microtrombidiinae Thor, 1935 is the largest subfamily in Trombidiidae. It consists of more than 50 genera, at least 300 species (Robaux, 1967). Womersley, Thor and Willmann, and Fe-ider revised Microtrombidiinae In 1945, 1947 and 1952 respectively. The structure and size of dorsal setae were generally used in classifying Microtrombidiinae before Feider, but Feider (1952) added the structure of palpal tibia in classification. Andre (1958) and Robaux (1967) adopted Womersley's (1945) and Thor and Willmann's (1947) classifications, referring to Feider's (1952) classification at the same time. The present paper described a new genus and a new species of Microtrombidiinae from China. The new genu is similar to Valgothrombium Willmann, 1940 but can be easily distinguished from the latter by its structures of dorsal setae and palpal tibia and tarsus.Falsivalgothrombium gen. nov. (figs. 1-7)Microtrombidiinae characterized by: Dorsal seta bifid at one third of its length from base, with barbs on all its length. Dorsal side of propodosoma with a rhombic plate, on which situated crista metopica and two pairs of non-pedunculate eyes. Crista metopica prolanged anteriorly, with a triangular naso anterior to its tip. At the posterior part of crista metopica is a rectangular sensillary area. Eyes very near to crista metopica. Palpal tarsus long, extending beyond the end of tibia claw. Dorso-internal side of palpal tibia with a comb, consisting of 5-7 short, thick spines.Type species: Falsivalgothrombium longitarsis sp. nov.Falsivalgothrombium longitarsis sp. nov. (figs. 1-7) Female: Idiosoma length 1650-1700 μm, width 1100-1200 μm. Dorsal side covered with a kind of setae bifid at one third of its length from base, with barbs on all its length. Dorsal setae 20-30 μm long. Dorsal side of propodosoma with a rhombic plate, on which situated crista metopica and two pairs of non-pedunculate eyes. Anterior pan of crista metopica longer than posterior part, but much weakly sclerotized. Sensillary area rectangular, with a pair of long, thin sensillae at its anterolateral corners. Slightly anterior to sensillary area are tow pairs of non-pedunculate eyes, very near to crista metopica. Crista metopica prolonged anteriorly, with a triangular naso anterior to its tip. All legs shorter than idiosoma. Tarsus I 280-320 μm long, about twice as much as its height (142-160 μm). Tibia I 160-180 μm long. Palpal tarsus long, extending beyond the end of tibia claw. Dorso-internal side of palpal tibia with a comb, consisting of 5-7 short, thick spines, with anterior spines thicker than posterior ones. Posterior to comb are many spine-like setae, not regularly arranged. Internal side of palpal tibia also with a few barbed setae. Fxternal side of palpal tibia with many barbed setae, also with a smooth long seta on its anterior dorsum. Palpal tarsus with many barbed setae, its anterior dor-sum bearing about 9 solenidions. Three pairs of genital suckers. Genital valve bearing around 23 smooth setae while paragenital valve bearing around 38 barbed setae. Anal pore posterior to genital pore. Anal valve bearing a few barbed setae.Male: unknowm.Type Locality: ColJrcted by the senior author in litter of Forest Park, Shanghai, on May 20, 1986. Hololype 1 female, Paratype 2 females, all deposited in the Department of Biology, Fudan University, Shanghai, China.Remarks: Of all the known genera of Microtrombidiinae, only Valgothrombium Willmann has a naso anterior to crista metopica. Similar to Valgothrombium, Falsivalgothrombium gen. nov. also has a naso anterior to crista metopica, hut it differs from Valgothrombium at least by the following features: (1) barbed dorsal seta bifid at one third of its length from base; (2) dorso-internal side of palpal tibia with a comb of 5-7 short, thick spines; (3) palpal tarsus extending beyond the end of tibia claw. Because the structures of dorsal seta and palpal tibia are key characters used in the classification of Microtrombidiinae, we consider it justifiable to create a new genus here.