THE CANADIAN ENTOMOLOGIST 283 



Pterocomma salicis (L.). 



Under this species Wilson discusses the forms determined as 

 salicis L. in this country. He concludes that the species does not 

 occur here, and considers the cornicle the distinguishing character. 

 While the cornicles figured by him are very distinct, the writer 

 has examined both American and European specimens in which 

 the cornicles are almost identical. They are not only the same in 

 shape, but the measurements are the same, and a range in variation 

 between the two types is met with in European material. It is 

 not probable that two European species are confused since the 

 variation was seen in aphides collected from one colony in France. 

 Another point of resemblance is the bright orange colour of the 

 cornicles in both European and American forms. It is true that 

 the cornicles of American forms seldom show the distinct bulging 

 met with in salicis, but with the variation in the European form, 

 and with the two forms showing the same measurements, it seems 

 hardly possible to separate them on this character of the cornicles. 

 Both European and American forms, moreover, show a more or 

 less distinct dusky bordering to the wing veins. 



In an attempt to find some other character to back up the 

 variation in the European cornicle and so to separate the American 

 form, the writer has measured a large series of apterous forms. 

 These have shown no differences. The European form shows 

 more variation in the antennal segments, the third segment par- 

 ticularly being sometimes longer in the European than in the 

 American form. In others, however, they are exactly the same, 

 and this is more often the case than otherwise. This variation in 

 the antennal segments does not seem to be, therefore, any definite 

 character upon which the two species can be separated with cer- 

 tainty. In the meantime, therefore, the writer prefers to hold 

 salicis for the American forms. 



Measurements of the alate viviparous female of both American 

 and European specimens will show their remarkable similarity in 

 this respect. * 



European: Antennee III, 0.72 mm.; IV, 0.464 mm.; V, 0.432 

 mm.; VI, (0.224 mm. +0.224 mm.); cornicle, 0.56 mm.; hind 

 tarsus, 0.256 mm. 



