June, "08] JOURNAL OF ECONOMIC ENTOMOLOGY 177 



no longer of service as food. During July winged individuals become 

 very scarce, but the winged lice soon appear in considerable numbers 

 and continue throughout the year. 



Identification of Species 

 Aphis gossypii Glover. 



Our observations upon this species continued for nearly a year be- 

 fore we were able confidently to separate it and medicaginis Koch, 

 from each other and from closely related forms. Some of the distin- 

 guishing characteristics which later enabled us to do this are the 

 following : 



In gossypii the black appearing apterous females are realh' a very 

 dark green; they nearly always have some light mottling upon the 

 dorsum of the abdomen, due to the light colored embryos showing 

 through, and these dark females are never highly polished. 



Fully mature apterous females have antennas and cornicles dis- 

 tinctly longer than in medicaginis. - 



The larvge of the first, second and third instars, especially of the 

 winged form, nearly always show a distinct yellowish brown or pale 

 salmon colored area upon the dorsal portion of the abdomen anterior 

 to the cornicles and a conspicuous dark transverse band at the cor- 

 nicles. 



There is nearly always much variety of color in both the young and 

 the adult apterous individuals, some being very dark, to the naked 

 eye appearing black, and others with intergrading shades passing to 

 very light yellow or tan colored viviparous females. The offspring 

 of these light individuals may be as dark as the darkest through their 

 entire life. 



The pupfB are beautifully tessellated over the dorsum of the abdo- 

 men with silvery white. 



So far as our observations have gone, gossypii has not been found 

 colonized upon so large a range of food plants as medicaginis, which 

 seems to be able to thrive upon almost any green thing. 



Sexual forms and eggs we have been unable to find. 



Aphis medicaginis Koch. 



The fully adult apterous viviparous females of this species we have 

 found, without exception, deep black and highly polished. They 

 shine like glass beads among the other lice of the colonies and may be 

 very few in number or entirely absent. 



2Care must be taken not to mistake immature individuals, just before the 

 last molt, for the fully mature form; they may be fully as large but they 

 have very much shorter cornicles and antennje. 



