BR. J. ENT. NAT. HIST., 6: 1993 



Karl, 1930) described it as a xerophile found on coastal dunes and in dry pasture, and 

 Vockeroth (1961) stated that it occurs on dry ground. Not all the English localities 

 conform with this preference for dry habitats. It is classified as nationally scarce (Falk, 

 1991). 



Geomyza balachowskyi Mesnil, 1934. There are several species in the combinata 

 group but only this species and hackmani have been recognized in Britain. These two 

 can be separated reliably only on the basis of the male genitalia which need to be 

 exserted so that the surstylar lobes are clearly visible. It is easy to mistake an 

 incompletely visible twisted lobe of balachowskyi for that of hackmani. There seem 

 to be no differences between the ovipositors of females caught in the same areas as 

 males of the two species. The colour of the postnotum is the same as, or only slightly 

 darker than, the rest of the thoracic dorsum. The wing width is 24-28% of its length. 

 Two males and a presumed female from St Kilda, Shetlands, have exceptionally small 

 and narrow wings, with the ratio of their width to length of 20-22%. The female 

 wing length is only 2.58 mm, which is smaller than any male measured. 



Geomyza annae Martinek and martineki Drake (which is the combinata of Martinek 

 (1978b) and Soos (1984)) are known from central Europe (Drake, 1992). These two 

 species differ from balachowskyi and hackmani in having slightly broader wings and 

 no shading at the end of vein M, but principally in their genitalia (Martinek, 1978b). 

 The combinata of Mesnil (1934) has similar genitalia and wings to those of hackmani 

 but has a long anepimeral seta like that of tripunctata; no-one seems to have confirmed 

 that such a fly exists. 



This species is widespread and moderately frequent in Britain and records extend 

 northwards to the Highlands. No habitat preferences are discernible in the records. 



Assuming that Nye (1958, 1959) was dealing with balachowskyi, he reared it from 

 Lolium perenne L.,Arrhenatherum elatius (L.) Beauv. ex J. & C. Presl, Holcus species, 

 wheat and barley. He cast doubt on the records of G. combinata larvae given by 

 Frew (1923) and suggested that they were probably G. tripunctata. Nye found that 

 the larvae overwinter in basal tillers, pupariate in April and emerge in May; they 

 probably have a second generation in July. However, dates of capture of adults (not 

 separated from G. hackmani) range evenly from the end of June to mid October. 



Geomyza breviseta Czerny, 1928. This and G. subnigra are the two British species 

 that always have dark thoraxes. Many specimens of G. tripunctata are dark but 

 their wing pattern makes them amply distinct. Geomyza breviseta closely resembles 

 G. subnigra but may be differentiated by its more chestnut-coloured thorax which 

 also has more pronounced metallic reflections on its paler parts, and in having less 

 contrast between the dusting on the thorax and abdomen. The apparently slight 

 difference in the shading of the costal cell beyond vein h does seem to be distinct. 

 However, all these characters are somewhat comparative and should not be relied 

 upon to identify isolated females unless the ovipositor is closely examined by slide- 

 mounting or viewing in alcohol; sternite 8 is apically emarginate in breviseta (Fig. 5f) 

 but produced to a narrow, faint point in subnigra (Fig. 5e). Males are easily distinguished 

 by the genitalia even if these are not exserted because the cerci are very small 

 in breviseta but in subnigra are similarly proportioned to those of tripunctata. 

 The dimensions of the wings and thorax are virtually the same in both species; the 

 differences in Fig. 1 are due to the specimens that were drawn being different sexes. 



Three other European species have dark thoraxes, so superficially resemble breviseta 

 (and subnigra). Geomyza paganettii Strobl and G. denigrata Czerny have broad wings 

 whose widths are about 34°7o of their lengths, and paganettii has four dorsocentral 



