52 MISCELLANEOUS STUDIES 



Group Aphidina Wilson 



Wilson, Ann. Ent. Soc. Am., vol. 3, p. 314, 1910. 



This group as considered by Wilson consists of three tribes: 

 Trichosiphini, Macrosiphini, and Aphidini. The first of these con- 

 tains two genera found only in the Asiatic islands, so it will not be 

 considered in this p'aper. This group contains quite closely related 

 genera, and in many cases it is quite hard to distinguish between 

 them. Following is a brief extract from Wilson's paper (cited above) : 



In studying closely related genera the development of the external characters 

 may be placed in five divisions: (1) the antennae and spur; (2) the antennal 

 tubercles; (3) the development of the nectaries [cornicles]; (4) the development 

 of the cauda; (5) the development of the wing venation. In a group of insects 

 as pliable as the present one, any one or two of these characters may be either 

 under- or over-developed and it is necessary to place the genera according to the 

 greatest development. Of all the characters which show this variation the wings 

 show what may be true of all these characters. 



The two tribes have been separated from one another on the character 

 of the antennal tubercles, as Wilson says in the same paper : 



The division is made between species with distinct antennal tubercles and 

 those having none or at the most indistinct tubercles. However, should a certain 

 species have distinct antennal tubercles with the other characters [of the Macro- 

 siphini] wanting, then it would have to go into the next tribe [Aphidini]. 



The keys to the tribes and genera below have been formulated by the 

 author, following, however, those of Wilson, Van der Goot, and 

 Mordwilko. 



1. Antennal tubercles well formed. Antennae usually as long as or longer than 

 the body. Apterae often with sensoria on the third antennal segment. 

 Body never with lateral tubercles on the seventh abdominal segment. Cor- 

 nicles variable but usually about one-fourth the length of the body or 



longer Tribe Macrosiphini 



Antennal tubercles absent or more or less indistinct. Antennae seldom longer 

 than the body. Apterae seldom with sensoria on the third antennal seg- 

 ment. Body with lateral tubercles on at least the seventh abdominal seg- 

 ment Tribe Aphidini 



Tribe Macrosiphini Wilson 



Wilson, Ann. Ent. Soc. Am., vol. 3, p. 314, 1910. 



To a large extent the author has followed Wilson in the placing 

 of the genera, but in a few cases he has not. This is noticeable in 

 Toxoptera, which is considered by Wilson as belonging to this tribe, 



