Anthomyza tschirnhausi, Rohacek, 2009

Roháćek, Jindřich & Barber, Kevin N., 2016, Nearctic Anthomyzidae: a monograph of Anthomyza and allied genera (Diptera), Acta Entomologica Musei Nationalis Pragae (suppl.) 56, pp. 1-412 : 277-278

The Anthomyza tschirnhausi group

The group is established here for three species of Anthomyza , the E. Palaearctic A. tschirnhausi Roháček, 2009 and two Nearctic species described below, A. shewelli sp. nov. and A. gilviventris sp. nov. ROHÁĆEK (2009a) tentatively associated A. tschirnhausi with the A. collini group but claimed that this afnliation is poorly supported because A. tschirnhausi is strikingly different from the other two (exclusively Palaearctic) members of the A. collini group. The A. tschirnhausi group can be diagnosed as follows (probable apomorphies, although sometimes not unique, are marked by A in parentheses): (1) t 2 with very short (posterior) ventroapical seta being paired with small (setuliform) to almost equally thick but shorter anterior seta (A); (2) epandrium high and narrow; (3) medandrium high, narrow and tapered dorsally (A); (4) hypandrium with distinct nat internal lobes (A); (5) postgonite very slender, elongate, directed ventrally and with 1 long nne seta; (6) basal membrane with lateral parts adjacent to caudal process of transandrium secondarily sclerotized and distinctly pigmented (A) (note: this character was apparently overlooked in A. tschirnhausi due to alcohol-fading of paratype male illustrated, see ROHÁĆEK 2009a: Figs 60, 62 ); (7) saccus with laterobasal lobe (bulge) (A); (8) nlum nnely spinulose along most of its length (A); (9) female postabdomen very narrow and elongate (A); (10) female tergosternum T7+S7 posteriorly tapered, long, very narrow, and somewhat laterally nattened (A); (11) T8 extremely narrow and elongate (A), with most of setosity reduced to microsetae or setiform sensillae and without micropubescence; (12) S8 (medially divided to form a pair of sclerites) also unusually long, narrow, devoid of micropubescence and with reduced setosity (A); (13) female genital chamber with one pair of very elongate sclerites besides the usual annular sclerite; (14) spermathecae subovoid and transversely striated, without terminal invagination; (15) female cercus with shortened setae and reduced micropubescence (the latter only on ventral side) and with apical seta exclinate (A).

The relationship of the A. tschirnhausi group has not been clearly denned; however, the formation of some genitalic structures (e.g. high medandrium, elongate postgonite, distinct caudal process of transandrium, and, particularly, the number and form of female internal sclerites) indicate that it may be more closely related to the A. gracilis group than to the A. collini group. Particularly, the nnely spinulose nlum of the distiphallus and the very elongate internal paired sclerites in the female genital chamber are the most distinctive synapomorphies linking the A. tschirnhausi and A. gracilis groups because they are unique within the genus Anthomyza . The afnnities of species within the A. tschirnhausi group are not very obvious because A. gilviventris more closely resembles A. tschirnhausi in the male genitalia (gonostylus in particular) while in the formation of the female postabdomen it more closely resembles A. shewelli . The Palaearctic A. tschirnhausi could possibly be a sister group to the Nearctic pair A. shewelli + A. gilviventris , if the more narrowed and prolonged female postabdominal sclerites with more reduced setosity are interpreted as synapomorphic in the latter pair.

Figures

Figs 60–65. Ischnomyia albicosta (Walker, 1849), female (Canada: Ontario, Figs 60, 64; USA: Tennessee, Figs 61–63, 65). 60 – postabdomen, dorsally; 61 – spermathecae; 62 – female internal sclerites, ventrally; 63 – ventral receptacle, sublaterally; 64 – postabdomen, ventrally; 65 – female genital chamber and S8, laterally. Scales = 0.05 mm (Figs 61, 63) and 0.1 mm (others). For abbreviation see p. 11.