(Figs 134, 135, 174, 175, 186)
Material examined. Holotype ♂, North Queensland, 25 km along Mt Lewis Road, SW of Mossman, 16.i.1977, M.S & B.J. Moulds, NMV.
Diagnosis. This species is grouped with Arc. tortula, Arc. flinti, and Arc. acmea in having the harpagones bifid, and sharing with Arc. acmea, Arc. tortula, Arc. volsella, and Arc. nebo the elongate, often sinuous apicolateral extensions on segment IX that extend beyond tergite X. It differs from Arc. acmea and Arc. tortula by the less robust genitalic structures and in ventral view the apicolateral processes club-shaped distally, rather than narrowly rounded or tapered to acute apices.
Description. Male. Length of each forewing: 8 mm (n = 1).
Genitalia (Figs 134–135, 174–175): Abdominal tergites IX and X fused, processes arising from lateromedial margins of segment IX elongate, bifid, reaching well beyond apex of tergite X, sharply curved upwards at about 1/ 5 length, in ventral view dilated distally, densely setose; tergite X broadly rounded, scarcely cleft midapically; gonopods each with coxopodite triangular to subrectangular in ventral view, in lateral view trapezoidal, harpago bifid; phallus without parameres, slender distally, widest medially.
Distribution. Known only from the type specimen from the Wet Tropics of north-eastern Queensland.