284 THE CANADIAN ENTOMOLOGIST 



American: Antennae III, 0.7 mm.; IV, 0.448 mm.; V, 0.384 

 mm ; VI, (0.208 mm. + 0.224 mm.); cornicle, 0.544 mm.; hind 

 tarsus, 0.24 mm. 



It will be seen fnim these measurements that the European 

 and American forms are the same as far as proportions are con- 

 cerned, and considering the great variation met with in the cornicles 

 of the European, and even of the American examples, there does 

 not seem sufficient basis in the writer's opinion for keeping the 

 species distinct. Certainly the two forms are much more nearly 

 alike than are the American form and bicolor Oestlund. 



Pterocomma bicolor (Oest.) 



The American specimens listed under this species by Wilson 

 do not, the writer believes, belong here. Oestlund gives the length 

 of cornicles as 0.85 mm., whereas Wilson gives them as 0.59 mm.; 

 fully equal to those of salicis. The following measurements of the 

 alate \i\iparous female made from specimens of bicolor collected 

 by the writer in Ontario show that Wilson's bicolor measurements 

 refer not to this species at all, but perhaps to variations of salicis? 

 The cornicles of bicolor are quite distinctive and the same as given 

 1)\ Oestlund in his description. 



Measurements of alate viviparous female: Antennic III, 0.672; 

 IV. 0.38 mm.; V, 0.30 mm.; VI, (0.16 mm. + 0.352 mm.) ; cornicles, 

 0.352 mm.; hind tarsus, 0.22 mm. 



It will be seen that this species is separated from popnlifolicB 

 by the proportions of segment VI of the antenna. The base is 

 much shorter and the unguis /nuch longer than in Fitch's species. 

 This character may not be a constant one, and in such case bicolor 

 will become a synon\m. In the National Museum collection there 

 are specimens determined as bicolor by Williams. According to 

 Davis (1911) this determination has been confirmed by Oestlund. 

 Williams' specimens in the collection are certainly popuHJolice. 

 The measurements of segment VI, of the two alate specimens 

 present are (0.176 mm. +0.288 mm.) and (0.176 mm. +0.27 mm.). 

 Comparing these with measurements of one specimen in Fitch's 

 collection, which measures (0.144 mm. +0.250 mm.), we see that 



