THE BUR CLOVER APHIS. 



27 



clover and a species of Oxalis. Mr. Sanborn has also noted it as 

 occurring on clover {TrifoUum hajariensis)^ cowpea, alfalfa, and coffee 

 bean ( Cassia occidentalis). 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 aj^his, the species is often so severely parasitized by 

 Lysiphlebus testaceipes Cress, that it is killed out in a very few days. 



The young stages and the apterous females are not at first easy to 

 distinguish from A. gossypli, 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 



Fig. W.—Apliia (jonsijijii: a. winged female: act, enlarged antenna of same; ab, dark female, side view; 

 b, young nymph or larva: o, 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 gossyplL These markings, however, are only noticeable when 

 the specimens are mounted in balsam. 



Specimens were determined as probably inedicaghus Koch b}" Mr. 

 Th. Pergande, w^ho, however, seemed to share our own doubt as 

 to their identit}^ 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 hav^e come from 

 Europe. Koch states that the species is hardly distinguishable from 



