8 E. B. Williamson and J. H. Williamson 



Sometimes the first cross-vein normally crossing Cug stops at Cua and does 

 not reach the hind margin. In such a case the basal cell posterior to 

 Cu, is the equivalent of two cells, and in counting cells posterior to Cug 

 this basal peculiarity reduces the number of cells by one, but has nothing 

 to do with the length or distal termination of CU2, thus introducing a 

 misleading factor in the description of Cuj. 



All measurements in this paper are in millimeters. Length of abdo- 

 men includes the appendages. The color descriptions of preserved speci- 

 mens, because of indefinite patterns and obscure markings, are not very 

 satisfactory and there is a possibility that they give a very imperfect 

 picture of the living insects. However our brief color notes, made from 

 fresh material, while certainly less complete than we now wish, indicate 

 no particularly striking differences between the living and preserved 

 individuals. Probably even in life, color patterns are obscure and in- 

 definite, and detailed descriptions would be difficult, tedious and more or 

 less incomprehensible. It is not impossible that some delicate and evanes- 

 cent colors, overlooked by us in our hurried note making of freshly caught 

 specimens, may be detected in the future by more leisurely and better 

 equipped students. It must be remembered also that an obscure or in- 

 definite color pattern may, by a slight increase of pigment, become sharp and 

 definite and that such increase of pigment may take place nearly at the 

 end of imaginal life and after sexual maturity has been attained. Abdo- 

 minal appendages of both sexes are measured in dorsal view from apex 

 of dorsum of segment 10 to' apex of appendages. The anterior lamina 

 is measured from the apex of the sternum of segment 1 to the apex of the 

 posterior process. Possibly better fixed points might be selected, as a 

 bending of the abdomen between segments 1 and 2, either dorsally or 

 ventrally, moves the basal point. But in measuring the length of the 

 expanded postero-ventral wing of the tergum of 2, and the distance from 

 its apex to the base of the segment, while the antero-ventral angle of the 

 tergum is theoretically an admirable fixed point, in actual practice it was 

 found that due to bending of the abdomen this angle was often concealed. 

 The valve is measured from the posterior angle of the basal plate of the 

 ovipositor to the apex of the valve. The form of the hind border of the 

 prothorax is described as seen in antero-dorsal view. And similarly the 

 mesostigmal lamina is described as seen in postero-dorsal view. 



Key to Groups and Species op Perilestes 



1. M g arising usually at the level of one cell before the stigma or more 



proximad. Abdominal segments 3-6 each with a pale postbasal ring or area 

 proximal to an extensive dark median area. Face similar in the two sexes, 

 dark to black, not sharply patterned, the anteclypeus if paler only slightly 

 so and not strikingly different from the labrum and postclypeus. Male 

 superior appendage with a basal dilatation ending on the inner border in 

 an acute spine. Blade of the second hamule slender, narrowly spoon-shaped 

 or tapering, if flattened the apical blade with its flat surface in the line of 

 the long axis of the abdomen; anterior lamina longer (1.5 or more), slenderer. 



