AND OTHER INJL'RIOUS INSECTS OE I907 AND I908. 185 



As the wings of the Aphididse are speciahed by reduction, it 

 seems probable that these abnormahties are generally reversions, as 

 they usually take the form of added veins or branches. There is 

 nearly always a distinct vein on the costal margin of the front wing, 

 and sometimes also of the hind wing, which, without question, repre- 

 sents the costa. The strong vein, posterior to this, is formed by the 

 fusion of the proximal parts of the veins of both the costo-radial and 

 the cubito-anal system. The thickened anterior margin of this vein 

 running from the base of the wing to the proximal end of the stigma 

 is the subcosta. The posterior margin of this vein, which is not 

 thickened except where it forms the posterior border of the stigma, 

 is the radius, while the stigmatic vein is the radical sector. The three- 

 branched vein, usually called the third discoidal, seems to me to rep- 

 resent the united cubitus and media. The first two branches counting 

 from the costal margin of the wing represent the media, and the third 

 branch represents the cubitus. The next two veins usually called the 

 second and first discoidals are the first and second anals, respectively. 

 The third anal is not present. 



As the wings of Aphididse become reduced the media disappears 

 and only the cubitus remains in Pciitphigus. In CJicruics, the cubitus 

 has disap])eare(l, and in Phylloxera dcprcssa, which represents the limit 

 of reduction in the front wing, the first anal has also disappeared. 



The most primitive hind wing, which is nearly the same as the 

 front \\ing of Phylloxera deprcssa, is found in Mclauoxanthns and 

 LacJimis. z^'hcrc the costa and subcosta are both present. In this 

 wing I think that the vein usually called the second discoidal represents 

 the radial sector, or that it corresponds to the stimatic vein of the 

 front wing instead of to the second discoidal. The other discoidal is 

 the second anal. The veins of the hind wing have probably been lost 

 in the following order : Subcosta, costa, second anal, radial sector. 

 So that the most reduced hind wing has only the unbranched radius. 



The Legs: The legs of the Aphididcc do not diiTer greatly 

 from the legs of other Homoptera. In the gall-makers and in the funda- 

 trix of some other genera the legs are very short. In the higher genera 

 the legs are long and slender. The extreme length of the hind legs in 

 these genera is correlated with their habit of kicking them up when 

 alarmed, that is, they are specialized as organs of defense. The coxa 

 in Aphids is small and has no trochantine. The short trochanter is 

 fused wath the femur. The suture between the trochanter and femur 

 is straight, but is oblicjue in Chcniics. In the lower genera the femur 

 is about as long as the tibia. In the higher it is_^only half as long. 



