212 Phoridae. 



of great importance and facilitates the determination. In measuring 

 the length of the costa and of the whole wing I follow Schmitz (Jaarb. 

 Nat. Genootsch. Limburg, 1917, 134) and measure from the long bristle 

 or hair at the base of the costa (it seems that Wood, judging from 

 his descriptions, has measiired in a similar way, perhaps simply from 

 the base of the wing); the costal divisions on the other hånd are meas- 

 ured from the humeral cross-vein and in the following way : division 1 

 stretches from the humeral cross-vein to the point where the inner 

 contour of the first vein joints the costa, division 2 stretches from 

 this point to the point where the inner contour of second vein, the 

 anterior branch of the fork, joints costa, and division 3 from this 

 latter point to the end of costa. The relative lengths of the divisions 

 may, to be sure, vary a little (and sometimes more considerably), 

 but when microscopical measurements upon the whole are used, we 

 may necessarily use quite fixed points. As to the terms long and short 

 regarding the costa I likewise follow Schmitz and take the border 

 between long and short as lying at 0,44 so that a costa reaching 0,44 

 of the wing-length or beyond is long, a costa not reaching 0,44 is short; 

 it might seem that this border is rather arbitrary, but experience has 

 shown that there really is something like a dividing line here. The 

 length of the costal cilia, whether short or long, is generally rather 

 easily determined, though also here intermediates and variation 

 may occur. 



Table of Groups. 



1. Scutellum with four or six bristles Group I. 



— Scutellum with two bristles 2. 



2. Mesopleura bristly 3. 



— Mesopleura bare 6. 



3. Mesopleura besides the small bristles with. one or more longer 

 bristles 4. 



— Mesopleura with only small, uniform bristles 5. 



4. Costa long Group II. 



— Costa short Group III. 



5. Costa long Group IV. 



— Costa short Group V. 



6. Costa long Groujj VI. 



— Costa short Group VII. 



Table of Species. 



Group I, 



Scutellum with four or six bristles. 

 1. Hind tibiæ simple, wåthout dorsal hair-seam or bristles 2. 



— Hind tibiæ with a dorsal hair-seam and bristles 3. 



