I02 Annals Entomological Society of America [Vol.11, 



given species and upon what plants at any time during the entire 

 season. This has given me a range of from 95 to 105 available 

 species belonging to at least 16 different genera and representing 

 all the types of venation in the entire family. 



At the Maine Station two insectaries (one an unheated build- 

 ing of use only during the summer, and one a hot house), have 

 both been available for the segregation of colonies of aphids taken 

 previous to the development of wing pads in order that they could 

 be used at exactly the right time. This made possible a large 

 amount of material safe from the depredations of predaceous 

 insects and parasites, a condition which could never' be relied 

 upon with chance collections in the open. 



In view of the fact that for the work in hand, no specimen 

 could be used for the study of wing tracheation except during the 

 first few minutes after emergence from the last molt, and that 

 the nymphs could be studied only during a very limited time 

 before the developing wings became much folded in the sac, 

 and that some species gave conspicuously better results than 

 others by virtue of such reasons as the slightly different angle 

 at which the wing pad of certain species are held, or to differences 

 in color, etc. : — it will be evident that the conditions outlined have 

 been most propitious for the study of this particular problem 

 with aphids. 



The reasons for approaching the homologies of the wing veins 

 of insects by a study of the tracheae that precede the veins were 

 so fully set forth and their validity so thoroughly demonstrated 

 by Comstock-Needham* ten years ago that this phase of the 

 question has long been too familiar to call for general discussion 

 here. 



However, with each new group of insects studied in this way 

 conditions exist which may have a special bearing on the subject. 

 For instance, an ontogenetic study of the wings of certain insects 

 is not of any value in determining the homologies of the veins| 

 in which case entire dependence must be placed on a careful com- 

 parison of the veins of the mature w4ng. 



On the other hand w4th wings so highly specialized by reduc- 

 tion of veins as those of the Homopterous group with which this 

 paper is concerned, the subject is a hopeless one to approach from 



* The Wings of Insects. Amer. Nat. XXXII and XXXIII, 1S9S and 1899. 



X MacGillivray, A. D., Wings of the Tenthredinoidea 1906. Proceedings 

 of the Nat. Museum. Vol. XXIX, page 574. 



