51 
group and any slight differences that may occur could as well be as- 
cribed to individual variation as to specific distinction. As we before 
remarked the most easily recognized points of differentiation between 
the species probably will be found to occur in the larvae and until these 
have been carefully studied and extensive breeding ex ova undertaken, 
all attempts at a thoroughly reliable classification must be more or less 
tentative; it is very probable that several alterations in the following 
arrangement will have to be made before stability is attained, but such 
things are unfortunately unavoidable in a group so imperfectly known 
as this one. 
Besides the material in Collections Barnes and Merrick (recently 
acquired by Dr. Barnes) we have had before us, with the exception of 
types, all the material from the American Museum, New York; Brook- 
lyn Ins. Museum; Field Museum, Chicago; Central Experiment Farm, 
Ottawa, Canada; Collections Chagnon, Cockle, Doll, Lacey and Winn; 
further through the kindness of Messrs. Grossbeck, Gerhard, Hamp- 
son, Johnson and Palm we have been able to secure photographs and 
valuable information concerning the types of species described by 
Grote and Robinson, Strecker, Walker, Palm and Packard. To all 
these gentlemen and institutions we would express our sincere obliga- 
tion; without their kind assistance this work would have been an 
impossibility. We regret deeply that owing to matters of a personal 
nature the Curator of the National Museum, Washington, has seen 
fit to refuse us any assistance either in the way of photographs or spec- 
imens; we had hoped the time had arrived when personal bickerings 
would be laid aside in the cause of science, but apparently we were 
too optimistic. 
