1910. : 249 



swollen in both sexes, those of the female being as thick as in male 

 manicafa and those of the male considerably more so, fully as thick in 

 fact as the tibiae. 



Hirsuta. — By no means so common as the precedinp; species ; it 

 occm-s at the same time with it and under the same conditions, and is 

 probably of wide distribution, for I have seen it from ISTewmarket and 

 I think from Bonhill also. The larg-e coarse hairs on the hypopygium, 

 combined with its deep l)lac]v colour and strongly bristled pleurae, are 

 rough and ready means of identifying it. 



In working through the species in this Section two points haye 

 forced themselves into notice. One is the frequency with which the 

 upper supra-antennal bristles are set wide apart and outside an align- 

 ment with the inner bristles of the middle frontal row, whilst the under 

 ones, generally nearly as large, lie close together and considerably below 

 them. It is especially among tlie smaller forms that this arrangement 

 prevails ; among the larger ones the bristles rather follow the pattern 

 most usual in the other Sections, in which the upper pair lie inside this 

 alignment, and the under pair, varying from large to minute, come 

 nearly directly underneath and close to them. The other and more 

 interesting point, since it illustrates the ready way in which the wings 

 adapt themselves to their mechanical needs, is the absence in these 

 short-costa species of a distinct curve at the commencement of the 1st 

 thin vein. In those with a long costa a greater or less cuiwe is gene- 

 rally present, in order seemingly to enable the vein the better to fulfil 

 its function as a support or buttress to the costa. That this is its 

 purpose here is, I think, shown by the fact that in the heavy female 

 the cui-ve is commonly Iwlder than in the smaller and lighter male. 

 Where, however, the costa is short, it is the long and weak portion of 

 the wing beyond that wants support, and so the 1st thin vein, instead 

 of bending downwards into the wing space, comes off straight or nearly 

 so, and acts as a sort of prolongation of the costa, including under the 

 term not the costa only but also its framework of thick veins. 



I have now passed systematically in review this huge complex of 

 a genus as represented in our British fauna. Great as is the number 

 of species here dealt with, many others there can be little doubt yet 

 await discovery or exist undescribed in collections. Several indeed are 

 even now known to ine, and 1 hope shortly to describe them in a Sup- 

 plement, which will at the same time be needed for some general 

 remarks, and for the correction of those errors that have come to light 

 whilst this article has been in progress. 



