Anu is distinguished from all other Syrphidae by the male terga reduced apicomedially so that the abdomen may be bent into an apicodorsal curve (almost always in dead specimens); the 1st tergum is divided into lateral plates as the medial area is entirely membranous; and the scutellum is concave apicomedially with the subscutellum greatly produced so as to be visible dorsally. In the last key to the genera of Syrphini (Vockeroth 1969), Anu runs to couplet #24. The statement about the scutellum in couplet #21 should be ignored; otherwise Anu agrees well with the rest of the first alternative. Anu is distinguished from both Exallandra and Sphaerophoria by the unique autapomorphic characters listed above (Thompson 2008).
Anu Thompson, 2008.
Thompson, F.C. (2008) A conspectus of New Zealand flower flies (Diptera: Syrphidae) with the description of a new genus and species. Zootaxa 1716, 1-20. [2008.02.29]
Adapted from original description (Thompson 2008).
Small slender flies. Length: 5–6 mm.
Head: Face straight, with distinct medial tubercle, yellow, with or without black medial vitta; oral opening about 1.5 times as long as broad; gena narrow; front not swollen, with slightly divergent side dorsally in female; antennal sockets confluent; eye bare, holoptic in male, with eye contiguity as long as ocellar triangle; antenna short, with basoflagellomere oval; arista long, about as long as antenna.
Thorax: Mesonotum yellow laterally from postpronotum (humerus) to transverse suture; scutellum slightly concave apicomedially so that subscutellum is visible dorsally; subscutellar fringe absent; anterior anepisternum bare; katepisternal pile patches broadly separated throughout; metasternum bare; metathoracic pile patch absent; postmetacoxal bridge absent; legs simple; plumula simple, short. Wing: hyaline, extensively microtrichose; vein R4+5 straight; vein M1 (apical crossvein) oblique, slightly sinuous; alula narrow, about as wide as cell CuP.
Abdomen: 1st tergum divided into lateral plates by membranous medial area; without marginal sulcus; male with terga 2-4 broadly membranous apicomedially, so abdomen is bent apicodorsally. Male genitalia: surstyles asymmemtric; lingula absent; paramere free; aedeagus two-segmented. Etymology: Anu is an arbitrary combination of letters and is to be treated as masculine.
Anu, along with Exallandra, Giluwea and Sphaerophoria (including Loveridgeana) probably form a monophyletic group characterized by yellow mesonotal vitta, loss or reduced subscutellar fringe, loss or reduced lingula, bare or reduced metasternal pile, and Anu is probably the sister to Giluwea as their genitalia are most similar (both have asymmetric surstyli) (Thompson 2008).
unless otherwise stated