BR. J. ENT. NAI. HIST., 6: 1993 167 



which may darken in dried specimens. The last section of vein R 4 . . may be 

 infuscated and this must not be confused with the separate spots of punctata. The 

 species typifies the group of closely related species which have very similar genitalia 

 in both sexes and the males of which have middle tibiae with simple chaetotaxy. 

 It is widespread in Britain and sometimes common in lowland areas but scarce 

 in western pastureland. It is a serious pest of wheat, barley and Lolium in Europe 

 and Russia (e.g. Slope, 1957) but the wild hosts are not known. Thomas (1933) 

 describes the life history. There is one generation per year. The eggs are laid on 

 the soil close to the base of a wheat stem in autumn and probably overwinter in this 

 stage, unlike nearly all other opomyzids studied which overwinter as third instar 

 larvae. The eggs hatch in spring, the larvae pupariate within the tillers in May and 

 the first adults emerge in early June. They are long-lived and move away from the 

 fields into woodland and hedgerows until October when they mate and return to lay 

 their eggs in arable fields. This account agrees with the dates of records which extend 

 from the beginning of June to early November with most occurring from August 

 to mid-October. 



Opomyza germinationis (L., 1758). There is a strong possibility that some of the 

 specimens in the Linnaean collection were muddled at some time because there is 

 a specimen of what we know as O. germinationis masquerading as the type specimen 

 of Geomyza combinata and the type specimen of germinationis is a species of 

 Palloptera (Brian Cogan, pers. comra.). Linnaeus's description of Musca germinationis 

 fits the species now known by this name rather better than the Palloptera or those 

 in the combinata group. Although germinationis is the type species of the genus 

 Opomyza Fallen, it would be prudent to retain the name Opomyza in the currently 

 accepted sense rather than attempt to redefine the genera Opomyza and Geomyza 

 on the basis of the Linnaean types. 



The characters used in couplet 2, together with the form of the genitalia, separate 

 germinationis and petrel into a group that is clearly different from the remaining, 

 predominantly yellow, British Opomyza. The abdominal pattern of occasional 

 specimens of germinationis may resemble that of petrel but then the central stripe 

 extends at least partly along the hind margins of the tergites, thus breaking up its 

 outline. In doubtful cases, the other key characters will separate them. Of many 

 hundreds of specimens examined, only one germinationis had several distinct 

 proepisternal setulae. A similar Opomyza from eastern Europe and Russia is 

 thalhammeri Strobl which differs from germinationis (and petrel) in having a 

 completely shining black abdomen and the costal shading starting beyond the level 

 of crossvein r-m. Two Macquart species, fuscipennis and fasciata, may be synonymous 

 with germinationis as they are not mentioned in Soos (1984) and no-one but Czerny 

 (1928) and Seguy (1934), neither of whom had evidently seen these species, makes 

 reference to them. 



Opomyza germinationis is probably one of the commonest British flies, being found 

 in a wide range of habitats throughout the country including Orkney. It is univoltine. 

 the eggs being laid usually near the base of the stems of host plants or on the soil 

 in early September to early November, the larvae overwintering mostly in the third 

 instar, pupating in May and emerging in June (Thomas, 1934). The larvae feed within 

 the stems of many species of common grasses (Thomas, 1934; Nye, 1958). 



Opomyza lineatopunctata von Roser, 1840. This unmistakeable small yellow fly is 

 the only one in the florum group with a thoracic stripe. Rarely, there are extra small 

 spots, with or without underlying crossveins, proximal to crossvein r-m, as in punctella. 



