Dichaetomyia Malloch, 1921

Couri, Marcia S., Pont, Adrian C. & Daugeron, Christophe, 2010, The Muscidae (Diptera) of New Caledonia 2503, Zootaxa 2503 (1), pp. 1-61 : 27-28

Genus Dichaetomyia Malloch

Dichaetomyia Malloch, 1921a: 163 . Type-species: Dichaetomyia polita Malloch, 1921 [preocc., = Dichaetomyia emdeni Pont, 1969 ], orig. des.

Diagnosis. Eyes of male narrowly separated by the diameter of anterior ocellus or more; eyes in female widely separated; proclinate orbital and crossed setae on frontal vitta absent; arista long-plumose; dorsocentrals 2+2, 3 or 4, the first presutural seta shorter than the second; prosternum setulose on sides; anepimeron setulose; prealar seta present; postalar wall with sparse hairs or bare; posterior spiracle with some black setulae along lower margin; vein M only slightly curved forwards before apex; hind tibia with a well developed anterodorsal preapical in addition to dorsal one, calcar absent.

Comments. Dichaetomyia is abundantly represented in the Australasian/Oceanian Regions, with 72 species ( Pont, 1989). Two species have been recorded from New Caledonia: D. bilimbata ( Bigot, 1885) , described from New Caledonia, and “ Dichaetomyia sp. polita -group”, listed by Shinonaga et al. (1991) which we describe here as new. Both species are endemic and belong to the polita -group (see Pont, 1969a). Nine species belonging to this group have been described from the Oriental and Australasian Regions. Six of these are from Malaysia and the Philippines, and two are from New Guinea ( D. polita (Stein) and D. nigrolineata (Stein) , the latter endemic so far as is known). Pont (1969a) described D. collessi from Australia (Queensland) which, according to him, “occupies a rather isolated position amongst Australian Dichaetomyia ”, being most closely related to the New Guinea D. polita .

Both New Caledonian species belong to the polita -group and share the following characters: male with two pairs of tiny reclinate orbital setae, and female with one strong pair of frontals near lunule and a weak pair above this; presutural acrostichal setae arranged in 9 to 10 series; dorsocentrals 2+3, the first presutural at least half as long as the posterior pair; meron bare but with fine hairs on metepisternum above hind coxa; anatergite bare; fore tibia with a submedian posterior seta; lower calypter bare on disc.

Dichaetomyia species , and especially D. bilimbata , appear to be by far the dominant muscid populations on the island and were mainly collected at Rivière Bleue.