THE BUR CLOVKK A Pills. 
27 
clover and a species of Oxalis. Mr. Sanborn has also noted ii as 
occurring on clover (Trifolium hajariensis), cowpea, alfalfa, and coffee 
bean (Cassia occidentals). Late in April it often becomes so abun- 
dant on bur clover as to cause the plant to wither, large swarms of 
flies buzzing around the infested plants attracting attention to them. 
Like the cotton aphis, the species is often so severely parasitized by 
Lysiphlebus testaceipes Cress, that it is killed out in a very few days. 
The } r oung stages and the apterous females are not at first easy to 
distinguish from A. gossypii, but the apterous females are darker and 
have a shining reddish or brownish-black appearance, while those of 
gossypii are deep greenish in color and have the cauda very much 
cut. 
Fig. U.— Aphis gossypii: a, winged female; aa, enlarged antenna of same: ah, dark female, side view. 
!>, young nymph or larva: c, last stage' Of nymph: d, wingless female— all greatly enlarged (after 
Chittenden). 
longer. The winged forms are readily distinguished by the dark 
markings on the abdominal segments of medicaginis which are lack- 
ing on gossypii. These markings, however, are only noticeable when 
the specimens are mounted in balsam. 
Specimens were determined as probably medicaginis Koch by Mr. 
Th. Pergande, who, however, seemed to share our own doubt as 
to their identity with that species. After a careful examination of 
Koch's description and figures, though there are some noticeable dis- 
crepancies, it nevertheless seems probable that our species is that 
described by him, especially as some of its host plants have come from 
Europe. Koch states that the species is hardly distinguishable from 
