mos.] 167 



cilia on the upper border of the hind tibiae. The size and number oi 

 these bristles vary greatly, but in opposite directions, that is to say, the 

 larger they are the fewer is their Dumber, and vice versa. Where 

 the legs are brown or black, it is so general a rule tor the front legs 

 to be paler that it will be unnecessary to refer to this detail in the 

 descriptions. 



For the sake of brevity I shall use the figures 1, 2, and 3 to 

 represent respectively the first, second, and third costal divisions. 

 1 would also point out that I take the first costal division lo be 

 the portion lying between the humeral cross vein and the inner 

 edge of the first thick vein, rather than the outer edge of this 

 vein — the more correct measurement. And for the reason, that 

 since the outer edge runs almost insensibly into the costa, whilst 

 the jun ion on the inner side is clear and definite, the eye 

 naturally selects the latter for the boundary. Nor is the point 

 so small as it looks, for on reaching the costa the vein usually expands 

 more or less, and it therefore makes quite an appreciable difference, 

 when dealing in such small dimensions, on which side of it the 

 measurement be taken. Further, the length of the frons is taken at 

 the margin of the eye, which usually gives a rather shorter measure- 

 ment than if it were taken up the centre. 



GEOUP II. 



Frons with a central channel ; two or four bristles at the base of the antennae, 

 directed forwards. Shaft of tibiae without spines, at most with rows of bristles. 



Second thick vein undivided. 



Section A. 

 Second thick vein divided. 



Scutellum with four or more hristles. 



Section B. 

 Scutellum with only two bristles. 



Costa long (to middle of wing or nearly) or very long (well beyond middle). 



Section C. 



Costa short or very short (from f, or a little over, to \ the wing length). 



Section D. 



SECTION A. 

 $ <j> . Thorax greyish, scutellum with four bristles ; abdomen black, short and 

 broad ; frons grey, about as broad as long, the bristles large and curiously 

 arranged, inner bristle of lower row placed close to the eye, below and scarcely 

 internal to the outer one, the under pair of supra-anteimal bristles small and 

 directed forwards, the upper pair directed backwards, simulating the inner 

 bristles of the lower frontal row as ordinarily found (fig. 1) ; antennae dusky 



