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



on Lolium species (Thomas, 1938; Nye, 1959). After feeding in the central shoot of 

 the grass stem, the larvae pupariate within it, overwintering mainly in the third (final) 

 instar. This is a pest species of ley, and the numbers of larvae may be markedly higher 

 in well fertilized leys than in those receiving low inputs of nutrients (Moore & 

 Clements, 1984). The larvae are parasitized by the braconids Chasmodon apterus Nees 

 and Phaenocarpa livida Haliday and the pteromalid Stenomalinus sp (Thomas, 1938; 

 Moore et al., 1986). 



Geomyza venusta (Meigen, 1830). This species superficially resembles balachowskyi 

 and hackmani in body colour and wing size but differs from them in crossvein r-m 

 being entirely pale, the wings being markedly broader (the width 27-33% of the 

 length), the thorax noticeably shiny and with brown marks outside of the postsutural 

 dorsocentral setae and a reddish or brownish tinge on the notopleura, and the 

 postnotum often being black, at least centrally. The male genitalia are distinctive but 

 the European species G. annae Martinek has similarly bilobed apices to the surstylar 

 lobes (Martinek, 1978b). That species has a small spot on the r-m crossvein like 

 balachowskyi. 



Although G. venusta has been infrequently recorded in Britain and Falk (1991) 

 classified it as nationally scarce, on the Continent it is a fairly common and widespread 

 though minor pest (Balachowsky & Mesnil, 1935, Soos, 1984). Its larvae have been 

 recorded from Bromus and they overwinter within the shoots (Balachowsky & Mesnil, 

 1935). Most of its British localities are chalk grasslands and it can be frequent in 

 this habitat (L. Clemons, pers. comm.; Allen, 1982). There are records from Kent, 

 East Sussex, Surrey, Hampshire, Hertfordshire, Buckinghamshire, Oxfordshire, 

 Cambridgeshire, Salop, Strathclyde and Grampian. Its flight period is from early 

 June to late August, with most records in July. 



Acknowledgements 



I am grateful to Dr Stuart Ball, Dr Bill Ely, Steven Falk, David Gibbs, Dr Tony Irwin 

 (Castle Museum, Norwich), Dr John Ismay, Dr Ian McLean, Roger Morris, 

 Ivan Perry, Del Smith and the Trustees of the London Natural History Museum for 

 the loan of specimens and for submitting records, and especially to Dr Vladimir Martinek 

 for the loan of several Geomyza from central Europe. 



References 



Allen A. A. 1965. Opomyza lineatopunctata v. Ros. (Dipt., Opomyzidae) in Surrey; with a 



note on two other species of the genus. Entomologist's Mon. Mag. 101: 109. 

 Allen A. A. 1967. Record of two further little-known Opomyzids (Dipt.). Entomologist's Mon. 



Mag. 103: 172. 

 Allen, A. A. 1977. Geomyza breviseta Cz. and G. venusta Mg. (Dipt., Opomyzidae) in west 



Kent, the latter confirmed as British. Entomologist's Rec. J. Var. 89: 221-222. 

 Allen, A. A. 1982. The recurrence in Britain (W. Kent) of Geomyza apicalis (Meig.) and G. 



venusta (Meig.) (Dipt., Opomyzidae). Entomologist's Mon. Mag. 118: 96. 

 Andrewes, C. H. 1964. Geomyza angustipennis Zett. (Dipt., Opomyzidae), a species new to 



Britain. Entomologist's Mon. Mag. 100: 167. 

 Audcent, H. L. F. 1950. Bristol insect fauna Diptera. Proc. Bristol Nat. Soc. 28: 80. 

 Balachowsky, A. & Mesnil, L. 1935. Les insectes nuisibles aux plantes cultivees . Vol. 1, 1137 pp. 



Paris. 

 Carles-Tolra, M. 1993. Three new species of Opomyzidae (Diptera) from Spain. Ent. Obozr. 



72 (2): 410-413 [In Russian]. 



