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



0.28 r 



■ 

 ■ • 



• • • 

 ■ • 



• ■ 

 ■ ■ ■ 



■ • • 



length of 

 second dc q.14 

 (mm) 



0.75 1.0 1.25 1.50 



length of thorax (mm) 



Fig. 6. Length of second dorsocentral seta (first postsutural) against thorax length for 

 Geomyza apicalis. Circles = females; squares = males. 



Geomyza apicalis (Meigen, 1830). The large apical wing spot, narrow wings and 

 clear r-m crossvein make this species moderately easy to identify but the variable size, 

 or even absence, of the first postsutural dorsocentral seta could lead this species to 

 key out as hendeli in the keys of Collin and Czerny. However, there are good grounds 

 for thinking that hendeli is merely a small form of apicalis. Measurements of the 

 first three dorsocentral setae of 27 specimens of two series of apicalis, from Egham, 

 Surrey, in the Natural History Museum, and from Blakeney, Norfolk, in the Castle 

 Museum, Norwich, and single specimens from three other localities, show that the 

 second (first postsutural) seta is shorter in smaller specimens (Fig. 6), although there 

 is still considerable variation in its length. As a proportion of the length of the third 

 (second postsutural) seta, the second seta varies from 24 to 80% , compared to the 

 nearby acrostichal setae whose lengths are 17-30% of that of the third dorsocentral. 

 The second dorsocentral of the smallest male in the Egham series could have easily 

 been overlooked, being only one-third as long again as the acrostichals. Further 

 comments are made under hendeli. The wing breadth as a percentage of its length 

 is 20.5% (range 17.1-22.8%) for both female and male. 



Two more European species would key out at couplet 15 in the key. Geomyza 

 pilosula Czerny looks more like G. balachowskyi and has only pilose aristae. Geomyza 

 virgata Czerny has only three dorsocentral setae but otherwise would appear to be 

 very similar although Czerny described the male genitalia as smaller than usual. 

 A male from Germany labelled virgata in the Natural History Museum looks like 

 G. apicalis and its genitalia are of the apicalis type. 



Geomyza apicalis has been recorded from Kent (Allen, 1982), London (Natural 

 History Museum, as hendeli), Hertfordshire (Natural History Museum, in Collin (1945) 

 as hendeli), Surrey, Essex (Collin, 1945), Cambridgeshire, Norfolk, Humberside, 

 Derbyshire (Kidd, 1954), South, West and North Yorkshire (Skidmore et al, 1985; 

 Vockeroth, 1961) and Northumberland. The habitats where G. apicalis has been found 

 include grazing marsh, a moist shaded clay slope with Equisetum and sparse grass, 

 mud under reeds by an estuary, dunes and a sewage farm. Martinek (1978a, quoting 



