THE CANADIAN ENTOMOLOGIST 281 



are now present in the National Museum collection: 9292, 9293, 

 9297, 9390 and 9301. A study of these specimens shows that 

 rtifiilus agrees with populifolice Fitch. Oestlund (1887) considered 

 Fitch's species to be a Chaitophorus, and so described his populi- 

 folice. Davis (1910) considered it an Aphis, and described another 

 species under the name. Both of these writers expressed doubt 

 as to their determination. In the writer's opinion, populifolicB 

 stands as a good species, easily distinguished from populea by the 

 relative lengths of the cornicles and tarsi. 



The measurements for the alate viviparous female of this 

 species average: Antennse III, 0.64 mm.; IV, 0.368 mm.; V, 0.336 

 mm.; VI, base and unguis (0.192 mm. +0.288 mm.); cornicle, 0.352 

 mm.; hind tarsus, 0.24 mm. 



Specimens taken on Popof Island, Alaska, and determined as 

 populea by Pergande, are certainly populifolicB. Pergande concluded 

 that both Kaltenbach and Koch were wrong in stating the cornicles 

 of popidea to be cylindrical, and he was of the opinion that, "in 

 fact, they are clavate." So, indeed, they are in popiilifolice, but 

 the cornicles of populea are very plainly cylindrical, and in this 

 regard Koch's figure is excellent and the descriptions of Kaltenbach 

 and Koch exact. The Pergande Alaska specimens, now in the 

 collection of the Bureau of Entomology, show the following 

 measurements for the alate viviparous female: Antennae III 

 0.656 mm.; IV, 0.4 mm.; V, 0.384 mm.; VI (0.208 + 0.384 mm.); 

 cornicles, 0.38 mm; hind tarsus, 0.25 mm. 



It will be seen that these measurements agree almost exactly 

 with those given by Wilson for populea. But he gives no measure- 

 ments of the hind tarsus. It will be seen also that these specimens 

 agree with populifolice Fitch, and it is the writer's opinion that 

 the specimens measured by Wilson M-ere specimens of populifolice 

 Fitch. Specimens of American populea show that species to be 

 very different from populifolice. This is most apparent in com- 

 paring the cornicles and hind tarsi. Measurements for the alate 

 viviparous female of this species are as follows: Antenna III, 0.608 

 mm.; IV, 0.256 mm.; V, 0.24 mm.; VI (0.128 mm. -f 0.144) mm.; 

 cornicles, 0.192 mm.; hind tarsus, 0.192 mm. These figures indicate 

 clearly the striking difference between the two species. 



