320 Mr. J. E. Collin's Confribution toivards knowledge of 



central brown stripe, pre-alar bristle shorter and finer, 

 abdomen less distinctly tessellated, and wings with postical 

 cross-vein more upright. 



1^. Head in profile with rather smaller eyes than in personata, 

 and these also rather narrower on the upper part with a consequent 

 slight modification of shape of frons when viewed from above; 

 thus the narrowest part of frons is nearer the ocellar triangle and 

 extends for a less distance. Fronto-orbital bristles, bristles on 

 vibrissal ridges and upcurved bristles on oral margin, all less numer- 

 ous. Thorax somewhat yellowish-grey with an ill-defined central 

 brownish stripe; tip of scutellum brownish. Acrostichals finer; 

 only two strong bristles on front part of thorax behind humeri and 

 between presutural dorsocentrals and notopleiu-al depression, 

 whereas in personata there are 3-4; the missing bristle being the 

 outer one immediately behind humerus ( ? true posthumeral) ; a 

 strong intrahumeral and presutural still present. Pre-alar bristle 

 shorter and finer (only slightly differentiated from the usual short 

 bristly hairs of disc). Prosternal plate between front coxae usually 

 but not invariably bearing a few small bristles. Abdomen much 

 less distinctly tessellated, and with the central brown stripe visible 

 from any point of view, whereas in personata with a certain incidence 

 of the light the stripe may even appear gi-eyish. Legs rather more 

 distinctly hairy than in personata, but less so than in obtusa ; chaeto- 

 taxy very similar to that of personata, thus the hind femora have 

 long distinct posteroventral bristles, especially about middle, but 

 the hind tibiae are rather more strongly bristled with 5-6 antero- 

 ventral short bristles, and much longer and more numerous bristly 

 hairs behind just before middle. There are occasionally two bristles 

 behind front tibiae. Wings with a very small but distinct spine at 

 mediastinal break in costa, which is absent in personata, and with 

 the postical cross-vein more upright. 



2. (Only a single specimen examined.) Eyes, if anything, very 

 sUghtly more widely separated than in personata; a distinctly 

 smaller number of bristles on oral margin of jowls. Thorax agree- 

 ing in characteristics with that of male. Abdomen with a bi-oader, 

 rather ill-defined, central stripe; bristles on hind-margin of last 

 segment strong and all almost equally distant from margin. Chaeto- 

 taxy of legs very much as in personata. Wings as in the male. 



Length 4-5-6'5 mm. 



The type of H. unistriala in Zetterstedt's Collection is a 

 single male with the hind legs missing, but ahnost certainly 

 identical with the species described above. There is 



