Limnohalacarus, WALTER, 1917

Bartsch, I., 2013, Freshwater Halacarid Mites (Acari: Halacaridae) From Madagascar. New Records And The Description Of A New Species, Acarologia 53 (1), pp. 77-87 : 79

Limnohalacarus novus Bartsch, 2013

Collecting data — Three females (slides), ZMH; south central Madagascar, Fianarantsoa, Ionilahy , small stream crossing the railroad east of village, 200 m; 15 Aug. 2001; coll. R. Gerecke and T. Goldschmidt. Two females (slides), author’s collection; northern Madagascar, Antisiranana , Antalaha , Marofinaritra , River Andranomenaheli , upstream confluence with River Ankavia (right affluent below MD 135 ), 70 m, 22.3°C, 0.009 mS/cm, riffle; 04 Nov. 2001; coll. R. Gerecke and T. Goldschmidt .

Diagnosis (female, Madagascar individuals) — Idiosoma pale; length 260 – 270 µm. Anterior dorsal plate hexagonal, slightly (1.1 times) wider than long. Ocular plate 1.4 times longer than wide, including sclerite with gland pore. Posterior dorsal plate 1.9 times longer than wide and 2.7 times longer than anterior plate. Setae equalling second pair of dorsal setae lacking. Ventral plates fused. Female genital plate with three pairs of perigenital setae and five to six pairs of acetabula, each genital sclerite with two or three subgenital setae. Gnathosoma 1.2 times longer than wide; rostrum short. Dorsal pair of maxillary setae wider than basal pair. Dorsal margin of second palpal segment arched, with small notch between setae. Pharyngeal plate extending close to basal margin of gnathosoma. Telofemur I 2.3 times longer than high. Leg chaetotaxy, from trochanter to tarsus (parambulacral setae omitted): leg I, 1, 4, 4, 6, 8, 5; leg II, 1, 4, 4, 6, 7, 4; leg III, 1, 2, 3, 4, 7, 4; leg IV, 0, 1, 3, 3, 6, 3. Ventromedial seta on tibia II and both ventromedial setae on tibia III bipectinate, all other setae smooth. All tarsi with spiniform basal lamellae. Tarsi I and II with pairs of doubled parambulacral setae, tarsi III and IV with pairs of singlets. Claw I with numerous slender tines. Claws III and IV with lamellar ventral process, each process with about four tines.

Remarks — Adults of the two species at present known from Madagascar can easily be separated because of (1) the shape of the ocular plates, including versus excluding the sclerite with the gland pore, (2) the ventral plates, separated versus fused to a shield, (3) the length of the rostrum, short versus elongate, and (4) the claws on tarsus I, with numerous long tines versus a few delicate ones. The size of the rostrum and the shape of claw I can be used to separate the nymphal and larval stages of the two species.

Distribution — Madagascar and Australia (Queensland) ( Bartsch 2013).