Halacarus fuscatus Bartsch, 1993

Bartsch, Ilse, 2011, Halacarus socius (Acari: Halacaridae), description of the male and diagnoses of species of the Halacarus actenos group, Zootaxa 2800, pp. 18-40 : 29

Halacarus fuscatus Bartsch, 1993

Halacarus fuscatus: Bartsch (1993b : 56–59, figs 7A–E, 8A–D; 2007b: 376, fig. 7F, G).

Diagnosis. Length of female 605–750 µm, of male 470–620 µm. Frontal spine triangular, moderately long; its length 0.4 and 0.1 times that of AD and idiosoma, respectively. Posterior part of AD short, linguiform and with wide, truncate margin. Pair of glp-1 at 0.7. Pair of ds- 1 in margin or slightly outside AD, setae distinctly posterior to level of glp-1. Ocular plate small, ovate, with cornea and canaliculus. Pairs of ds-5 and ds-6 medial to and distinctly removed from glp-4 and glp-5, respectively. Anterior margin of female GA wide, rounded. Pair of pgs-1 slightly closer to margin of GA than to level of end of PE; its distance to anterior margin of GA equalling 0.4 times interval between margins of GA and GO. Male GA widest in middle of plate. One pair of pgs within striated integument, about 120 pgs around GO.

Gnathosoma 1.7 times longer than wide. Rostrum longer than gnathosomal base, extending to end of P-2. Basal seta on P-2 at 0.6. Spine on P-3 blunt. Epicuticula on legs delicately reticulated. Trochanters I to IV with 1, 1, 2, 1 setae, basifemora I to IV with 2, 4, 2, 2 setae. Telofemur, genu and tibia I with 2, 2, 4 spiniform and tapering ventral setae. Basalmost ventral seta on telofemur I at 0.4. Ventromedial seta on genu II and posterior one of ventromedial setae on tibia II bipectinate. Tarsi I to IV with 2, 1, 1, 1 ventral setae; tarsi III and IV with four (rarely three) and three dorsal setae. Paired claws with large accessory process, each with a cluster of about 12 tines.

Remarks. The integument of the legs of H. fuscatus is yellowish-brown, a colour unusual amongst Halacarus species.

Distribution and ecology. Australia, Western Australia, Rottnest Island and Esperance. The species lives amongst the epiflora of seagrass, algal fronds and sponges.