GALL APHIDS OF THE ELM. 23I 



tion. Many specimens of americana taken July i, 1909, in 

 Maine attain 7 mm. wing expanse). i: 



2. 'With iilmi the abdomen, wing veins, and stigma are 

 darker.' (This difference might perhaps be accounted for by 

 the difference between newly molted and aged individuals). 



3. 'With iilini the terminal distance between ist and 2d dis- 

 coidals is slightly greater.' 



4. 'With idmi the 3rd joint of antennse is relatively longer; 

 the annulations are less deep and more numerous, — those on 

 3rd joint averaging 30.' (A Maine collection of americana 

 of July I, 1909, have III with a range of from 24-30 annula- 

 tions. Professor Gillette figures this species with 35 annula- 

 tions). 



•5. 'With idmi joints 5 and 6 are smooth, i. c, without annu- 

 lations, but they are more setous.' (Maine collection of ameri- 

 cana of July I, 1909, have V and VI smoother than Riley's 

 figure, VI being indeed with no annulations and V having 2 to 

 7 and these not completely encircling the antenna). 



6. 'With ulmi joint 5 is shorter than 4.' (This is also the 

 case with the aforesaid Maine collection of americana). 



7. 'With iilmi the apical, narrowed part of 6th joint is rela- 

 tively longer and more pointed.' 



8. 'With ulmi the subcostal vein of hind wings is less 

 straight.' 



9. 'With ////;// the cubital vein (M) is often continuous to 

 very near the subcostal, while I have not found any tendency 

 of the kind in americana, the tendency being in the opposite 

 direction, or to become shorter.' (Maine 1909 material of 

 americana has wings very uniformly like fig. 152, (comp. Buck- 

 ton's figure of idmi), and no wing wath M as figured by Riley. 

 "Cubital vein of fore wings obsolete for some distance at base,, 

 rarely traceable its whole length." O. W. Oestlund, Aphid. 

 Minn. p. 27, 1887). 



10. 'With idmi the 2nd discoidal of hind wings shows a 

 tendency to fork.' ("Freak" venation is not uncommon with 

 aphids). 



1 r. 'A\'ith ;//;///' the booklets on costa of hind wings are 3 

 in number, while in americana there are normally 4.' ("Those. 



*For measurements of americana see comparison with rilcyi footnote- 

 page of this bulletin. 



