1906.] 241 



lomyia and its allies have the 7th or axillary vein curved in a peculiar 

 manner round the end of the Gth, while here again and in the remain- 

 ing group {Coenosla and its allies) there are only three post-sutural 

 dorso-central bristles. 



The species known to occur in Britain may be identified by Jneans 



of the following keys • — 



MALES. 



1. Hind femora wilh a single or double ventral spine 2 



Hind femora without ventral spine 5 



2. Spine of hind femora near base 2. occulta, Mg. 



Spine of hind femoi'a at or a little beyond middle 3 



3. Eyes thickly haired \. cUiata,'Pab. 



Eyes bare 4 



4. Spine of hind femora single 8. armipes,'F\n. 



Spine of hind femora double 9. albiputicta, Ztt. 



5. Abdomen yellow and translucent on at least the two basal segments... 



16. ctirvipes, Fin. 

 Abdomen nowhere yellow 6 



6. Wings with a patch of niicroscopic hairs at end of discal cell... 



10. militaris, Mg. 

 Wings without such patch 7 



7. Basal joint of middle tarsi with a cushion of short, stiff bristles... 



15. irritans, Fin. 

 Basal joint of middle tarsi simple 8 



8. Middle tibiae with 1-2 anterior bristles 9 



Middle tibiae without anterior bristles 11 



9. Small species (3^ —4 mm.) 18. parva, Meade. 



Larger species (6 — 8 mm.) 10 



10. Eyes almost touching ; hind tibiae with a median postero-ventral tuft of fine 



hairs 7. pUipes, Stein. 



Eyes distinctly separated ; hind tibiae without such tuft... 



6. palssstrica, Mg. 



11. Small species (3 — 3^ mm.) ; abdomen shining black, and at least the two apical 



segments without trace of tomentum 17. glabricula, Fin. 



Larger species (5 — 9 mm.) ; abdomen always more or less covered with to- 

 mentum 12 



12. Eyes thickly haired 3. cyrtoneurina, Ztt. 



Eyes bare 13 



13. Middle tibiae with regular fringes of fine hairs on anterior and posterior surfaces . . . 



11. tuberculata, Rond. 

 M iddle tibiae without such fringes 14 



14. Hind tibiae with 6 — 12 antero-ventral bristles 5. similis, M.ea.Ae. 



Hind tibiae with 2 — 3 antero-ventral bristles 4. dentipes, Fab. 



Hind tibiae with only 1 antero-ventral bristle 15 



15. Teeth on front femora inconspicuous and blunt 12. velutina, Dsv. 



Teeth on front femora long and very acute 16 



16. Thorax entirely black ; abdomen dark, with the dorsal stripe very indistinct... 



13. meteorica, L. 

 Thorax, when viewed from behind, with its posterior third distinctly cinereous ; 

 abdomen light cinereous ; with the dorsal stripe sharply defined ... 



14. cinerea, Dsv 



