Anthomyza gracilis Fallen 1823

The Anthomyza gracilis group

The Anthomyza gracilis group was erected by ROHÁĆEK (2006a) to include two Palaearctic species, A. gracilis Fallén, 1823 and A. elbergi Andersson, 1976, and was characterized by several apomorphic features, two of which were considered strong synapomorphies by ROHÁĆEK (2009a), viz. the peculiar dentate ventral appendage of the caudal process of the transandrium (Figs 18–21, 530–532) and the spermathecae with a long digitiform invagination (Figs 29, 32, 540, 541). In the Nearctic Region three more species belonging to this group were found that are described below as A. furvifrons sp. nov., A. vulgaris sp. nov. and A. equiseti sp. nov. These additions have not necessitated substantial modincation of the diagnosis of this species group which includes the following apomophic characters (unique synapomorphies marked with U in parentheses behind the character): (1) body densely grey to brownish grey microtomentose and largely dull; (2) medandrium high and narrow; (3) dorsal internal sclerite at base of postgonite usually large and bearing some spines; (4) caudal process of transandium ventrally with large toothed appendage (U); (5) aedeagal part of folding apparatus with clusters of dark spines, different on each side (U), cf. also Figs 15, 22; (6) female T7+S7 ventrally with desclerotized area that is often widened anteriorly; (7) paired internal sclerites in female genital chamber large, long and nat; (8) spermathecae with long digitiform invagination and eccentrically inserted duct (U); (9) female T10 with 1 pair of long setae and a few shorter setae in addition.

Based on morphological data, the A. gracilis group seems to be most closely allied to the A. tschirnhausi group (as denned here, see above). This relationship is supported by the following (obviously apomorphic) characters: medandrium high; postgonite slender and elongate; caudal process of transandrium strongly sclerotized; female T8 long and slender; and, particularly, female genital chamber with paired internal sclerites very elongate.

Two clades can be recognized in the A. gracilis group. The nrst includes both Palaearctic species (A. gracilis, A. elbergi) plus the Nearctic A. furvifrons sp. nov. (synapomorphies: aedeagal part of folding apparatus with strong spines also ventrally; internal paired sclerites in female genital chamber doubled), while the second includes only two Nearctic species, A. vulgaris sp. nov. and A. equiseti sp. nov. (synapomorphy: female T7+S7 ventrally with posteromedial lappet-shaped appendage). Additional notes on relationships for Nearctic taxa are elaborated upon below under each species. The most interesting of them appears to be the sister-species pairing of A. furvifrons and the Transpalaearctic A. elbergi.

Notes. Anthomyza gracilis has been repeatedly recorded from the Nearctic Region (see MELANDER 1913; JOHNSON 1925; PROCTER 1946; SABROSKY 1965; COLE 1969; ARNETT 1993, 2000; FOOTE 2002). Because this Palaearctic species has not been connrmed as occurring in North America in this study of the holdings of major North American collections, all these records must be based on misidentined specimens of other species of the A. gracilis group (i.e. A. furvifrons, A. vulgaris) or of members of the A. pallida group (i.e. A. concolor, A. vockerothi) and the A. tschirnhausi group (i.e. A. shewelli) as evidenced by determination labels listed in the respective sections on paratypes or material examined.

The illustration of an adult male Anthomyza gracilis in the Manual of Nearctic Diptera, Vol. 2 (VOCKEROTH 1987: Fig. 75.1), which was also used in ROHÁĆEK (1998b: Fig. 22.1), was based on European specimens but unfortunately not of true A. gracilis. They represent A. collini Andersson, 1976, which belongs to a species group not occurring in the Nearctic Region. This shortcoming results from the fact that, before ANDERSSON’ s (1976) revision, A. collini had been misunderstood to be A. gracilis, while the true A. gracili s had been recorded under the synonymous name of A. sordidella (Zetterstedt, 1848) (for more detail see ROHÁĆEK 2006a). The CNCI specimens [England: Devon: Newton Abbot, 22.vi.1960, 1 ♂ (genit. prep.) and Sweden: Sk: Bjerred, 2 ♂♂ (1 ♂ genit. prep.), 29.v.1951, all J. R. Vockeroth leg.], upon which R. Idema based his illustration in VOCKEROTH (1987), have been examined and they all belong to A. collini.