286 Orthorrhapha brachycera. 



the disc is uniformly clothed with short hairs which may be more or 

 less distinctly divided by two bare or \veai<:er haired stripes into 

 dorsocentral and acrostichal hairs. One to three notopleural bristles 

 and a poslalar bristle present, generally also a humeral, and some- 

 times a posthumeral bristle. Sciitellum has two or fom- marginal 

 bristles, in the first case the lateral bristles are represented by a 

 small hair on each side. Metapleura without hairs. Abdomen con- 

 sists of eight segments, but in the male the eighth dorsal segment 

 is hidden; the first segment is short, and weakly chitinised on the 

 ventral side. The male genitalia are more or less knob-like; they 

 consist of a large arched plale lying ventrally ; on the left side there 

 is a lamella-shaped piece, and above there is a pair of more com- 

 plicated pieces, which are more or less hidden by the two other 

 pieces; the lamella on the left side has a row of long, downwards 

 hanging hairs at its lower margin. In the female the abdomen is 

 pointed, the two last (seventh and eighth) segments are narrower 

 than the others and form an ovipositor, terminating with two small 

 styles; these two segments are generally of a duU grey colour in 

 contrast to the other, black, shining segments. The legs are rather 

 characteristic; they are strong, the front coxæ are very slightly longer 

 than the posterior coxæ ; the front femora are more or less thickened, 

 and the middle femora still more; the middle 

 tibiæ are shorter than the femora, and terminate 

 on the ventral side with a strong, downwards 

 curved apical spine; the front femora have two 

 rows of fine bristles below; the middle femora 

 have two rows of black, short, almost tubercle- 

 shaped spines below, and outwards to them on 

 the postero-ventral side a row of fine bristles; 

 the middle tibiæ have a row of black spines 

 Fig 131. T.flavipes, below, similar to those on the femora, but a 

 ^' '■ little longer and with a fine apex; the middle 

 tibiæ are adapted to be laid up between the rows of spines on the 

 femora, and also the front legs aet in a similar way; on the anterior 

 side of the middle femora towards the apex there are a few bristles. 

 For the rest the legs are short-haired, at most with a few small 

 bristles on the dorsal side of the front and hind tibiæ, and stronger 

 hairs below the hind femora. Tibiæ without apical spurs. — Such is 

 the ordinary shape and armature of the legs, but there may be some 

 variations. In some cases the anterior femora are almost not thickened, 

 the front femora sometimes not at all; the apical spine on the middle 

 tibiæ may be small or quite wanting; sometimes there are no long 



