124 DURHAM DIPTERA. 



XXIII. 217. 



217. Chersodromia, Wlk. 



Life history unknown. Shore species. 



1 (6). Black species. 



2 (5). Small species, less than 2 mm. 



3 (4). Wings very short, brownish white along hind border, 



veins black, legs stout. 

 1130. Chersodromia arenaria, Hal. 

 Hesleden, 2 $ and 2 $, August, 1900. Common, but 

 very difficult to catch, as they run rapidly among 

 the stones and sand. 



4 (3). Wings clouded ; veins brown ; hind tibiae bristly. 



(1131. cursitans, Ztt.) 



5 (2). Large species, 3^ mm. ( II 3 2 ' hirta, Wlk.) 



6 (1). Hoary species. 



7 (8). Legs brown ; very small species, % mm. 



(1133. incana, Wlk.) 



8 (7). Legs yellow. Pleurae with a black round shining 



spot above the middle coxae. Larger species, 

 2 mm. ( II 34' speculifera, Wlk.) 



218. Tachydromia, Mg. 

 Life history unknown. 



1 (9). Dorsum all yellow, or yellow with a black stripe. 



2 (6). Dorsum and abdomen all yellow. 



3 (4) (5). Head yellow, wing veins black. (1135. lutea, Fin.) 



4 (3) (5). Head hoary, wings colourless, veins tawny, very 



pale species. ( XI 36. glabra, Mg.) 



5 (3) (4). Head hoary, silvery white in front ; wings yellowish, 



especially along the fore margin ; veins yellow. 



(1138. flavifiennis, Wlk.) 



6 (2). Dorsum with a black stripe, abdomen dark. 



7 (8). Abdomen brown or black, sometimes tawny beneath, 



but without hoary bands. (1137. pectoralis, Fin.) 



8 (7). Abdomen black with four broad hoary bands. 



(1140. pulchella, Wlk.) 



9 (1). Dorsum not yellow. 



