No. 402.] THE VENATION OF TRIMEROTROPIS. 473 
In the tegmina C. and Sc. are simple veins which do not 
vary in such a manner as to be readily noted; the former is 
about halfway between the anterior margin and the three suc- 
ceeding veins, which are so closely approximate on the proxi- 
mal half of the tegmina as to appear one vein to the unaided 
eye. MR. is quite variab!z, though R., does not share in this 
variation. Æ., has normally three branches in the male and 
four in the female, but of the fifty-seven specimens examined 
six males have four branches and one male has two, and eight 
R 
females have three branches; thus about 24 per cent show 
irregularity in this respect. Within the genus the variation 
which normally occurs in the number of branches of œ. i 
exactly the same; within the subfamily the range is inis 
ably greater, being but one in Celes and six in Pachytylus, 
both old-world genera. In a single instance the apical part of 
R.s with two branches has lost its connection with the basal 
part with one branch, and the former is separately connected to 
R., (Figs. 3 a, 3 b). 
No similar variation is normal in the genus nor within the 
subfamily, so far as I know. The second branch of A., may 
