1901.] 107 



Humeral aud prothoracic bristles present ; usually five pairs* of 

 outer dorso-central bristles on the thorax, one pair being in front of 

 the suture (in oculata only three pairs are strongly developed). 

 Eyes larger than usual. Third antenna! joint large and rounded, disc- 

 shaped, vrith a moderately long, microscopically pubescent, arista. 

 Legs long and slender, with only the front femora at all bristly ; 

 prse-apical bristles very 



small. Wings (fig. 1) ^„ ^ ^''^"~ ^!~~^^^^^^^-Ti.__~rTTr^^^ 



large and long, the spines /^ ^____------^^^^P^ 



on the costa present, but nT^ ^ \^^-'^^/^vf^ '■ 



very minute; stigma elong- ■•-.. \ ^^..^^'-"'''^ / ■ lm'<''" 



ated. the first longitudinal "-^^ / ,^^ 



(subcostal) vein being Ym.\.-H.rot^^^^rns^Z 



continued beyond that point of the costa opposite the middle (discal) 

 cross vein. 



Additional characters in the male only. 'Eijes much larger than 

 in allied genera, and more approximated on the frons, both of which 

 characters are sometimes remarkably developed ; jowls very small, and 

 sometimes the face exceedingly narrow. Abdomen long, very narrow, 

 and very bristly, with inconsjiicuous genitalia. 



The complete chaetotaxy of the genus is as follows : — 



Head. — Two pairs of strong vertical bristles situated immediately behind the 

 top corners of the ejes, the inner pair convergent, the outer divergent. 



One pair of postverlical bristles rather small and convei'gent, situated just 

 behind the ocellar triangle. 



One pair of ocellar bristles on the ocellar triangle, which point forwards and 

 slightly diverge. 



Two pairs oi fronto-orlital bristles which point backwards and slightly out- 

 wards, tlie lower pair being the weaker (in II. oculata, S , these bristles are absent 

 because the frons is so very narrow). 



One pair of vibrissce and a row of small bristles after each vibrissa along the 

 sides of the mouth opening. 



One genal bristle on the jowls below the eyes conspicuous among the other 

 minor bristles present. 



Thorax. — One humeral bristle. 



Two posthumeral bristles {notopleural of Girschner and Becker)t situated in a 

 line with the humeral immediately above the dorso-pleural suture and in the post- 

 humeral depression. 



One prcBsutural bristle situated immediately in front of the thoracic suture and 

 almost in a horizontal line with the front posthumeral bristle. 



* Loew, in his description of the genus, certainly gave it as possessing only four pairs of 

 outer dorso-central bristles ; I think Loew must have overlooked the fifth pair, which are some- 

 times rather small, but I do not put much trust in this as a generic character, and should not 

 be at all surprised to find a Heteromyza possessing only four bristles of the outer dorsal row. 



t In his paper on 6catomu:id« Becker uses the terra potthumeral. 



L 2 



