Xenophytomyza Frey

Boucher, Stéphanie, 2003, The New World species of Cerodontha (Xenophytomyza) Frey (Diptera: Agromyzidae), Zootaxa 178, pp. 1-8 : 2

Subgenus Xenophytomyza Frey

Cerodonta (Xenophytomyza) Frey, 1946: 51 (Type species: Haplomyza atronitens Hendel, 1920 , orig. des.)

Diagnosis.­ Members of the subgenus Xenophytomyza can be distinguished from other subgenera of Cerodontha by their angulate first flagellomere, the presence of only one pair of scutellar bristles, mostly or entirely brownish­black body and by the distal tubules of the phallus which are fused or partly fused ( Figs. 2 , 6). The closely related subgenus Cerodontha s.s. also has only one pair of scutellar bristles, the first flagellomere is angulate (or with a spine at the anterodorsal corner) and some species have the distal tubules of the phallus fused or partly fused, but they always have more extensive yellow on the body ( Boucher 2002).

Distribution.­ Xenophytomyza is almost exclusively Holarctic. The Palearctic species have a boreal­montane distribution. Most European species occur in the nemoral zone, broad­leaved transitional forest between boreal forest and steppe. The eastern Palearctic species are more often associated with boreal forest, while the middle Asian species are exclusively found at high elevations (V.V. Zlobin, pers. comm.). In the Nearctic, however, Xenophytomyza species occur mainly in lowland areas, often in mesic grasslands and disturbed habitats, including forest paths, public parks and roadsides.

Host plants.­ As far as is known, all Cerodontha species are miners on Monocotyledoneae. Only three species of Xenophytomyza have known host plants, all in the family Poaceae ( Tschirnhaus 1991, Zlobin 1993).

Remarks.­ All species in the subgenera Xenophytomyza and Cerodontha lack the basal scutellar bristles present in other Agromyzidae ; the absence of these bristles is an apomorphy that supports a sister group relationship between these two subgenera. However, so far there are no well­supported apomorphic characters defining each of these subgenera. The absence of the funnel (“Trichter”) at the tip of the phallus used by Nowakowski (1973) to characterize Xenophytomyza (in addition to the form of the first flagellomere and the dark colour) is not a valid character, since the structure is present in C. (X.) biseta ( Zlobin 1993) . Dempewolf (2001) found no apomorphies to separate exemplar species of Cerodontha s. str. ( C. hennigi Nowakowski and C. denticornis (Panzer)) and Xenophytomyza venturii . Species­level relationships within this monophyletic group are not well­resolved and it is not yet known whether each of the two subgenera is monophyletic. A final decision on the status of these two subgenera will require a phylogenetic analysis of all included species. Published records of Xenophytomyza species with weak basal scutellars refer to a species now assigned to the subgenus Poemyza Hendel ( Zlobin 2001).

Figures

FIGURES 1 – 3. Cerodontha (Xenophytomyza) biseta (Hendel). 1, phallus lateral view (Jamaica, LEM); 2, phallus ventral view (Jamaica, LEM); 3, wing showing infuscation at junction between C and R 1. FIGURES 4 ­ 6. Cerodontha (Xenophytomyza) illinoensis (Malloch). 4, phallus lateral view (White Heath, IL, specimen # 12252, INHS); 5, phallus lateral view, variation (White Heath, IL, specimen # 12253, INHS); 6, phallus ventral view (White Heath, IL, specimen # 12253, INHS)