1908] Studies on Aphididae 259 



The Red-clover Aphis (Aphis bakeri Cowen). 



While examining the base of a rcd-clo\-er plant (Trifolium 

 pratense) August 5, 1907, at Urbana, 111., I noticed a colony of 

 immature pinkish aphids, which were apparentl}^ being attended 

 by the large black ant (Formica fusca L.) The aphids w^ere upon 

 the undersides of the stems close to the ground, and the ants had 

 built a roof-like structure, composed of debris, over the stems, 

 evidently for the protection of the aphids. The young aphids 

 above mentioned were reared to adults and successive genera- 

 tions obtained. In the fall, an infested clover plant was placed 

 in the cold insectary room — -this having approximately the out- 

 of-door temperature — where it remained until the middle of Jan- 

 uary, 1908. When examined at this date only pupa? were found, 

 and these, when brought into a warm room, became winged and 

 produced young. I have also found this species at Leroy, 111., 

 September 9, on T. pratense, and situated on the plant as were 

 those found at Urbana, but they were attended by another species 

 of ant (Cremastogaster lineolata Say) . During 1908 I have found 

 this species very common in fields and along roadways, on T. 

 pratense and attended by several species of ants, namely, Lasius 

 niger var. americanus, and the two species mentioned above. 

 Here the aphids commonly infested the upper parts of the stems 

 and the flowers, as well as the stems near the base. 



Several generations were carried through in the insectary, 

 and the following life-history notes taken : The number of young 

 produced by an individual female was found to vary from 61 to 

 72, giving an average of 2 to 3 young per day, the largest number 

 of young produced by a single female in one day being 7. Usually 

 the female lives 6 or 8 days after the birth of the last young. 



Because of the pinkish color of the immature individuals and 

 the pseudo-subterranean habit, I determined the species tenta- 

 tively as Aphis trifolii of Oestlund, which, in the original des- 

 criptions was characterized as a subterranean species found on 

 Trifolium repens L., and with a pinkish color, no other definite 

 characteristics being given. I sent specimens to Prof. O. W. 

 Oestlund who examined them and wrote to me that he believed 

 them to be the same species described by him some twenty years ago, 

 and named Aphis trifolii ; though he had never seen the adult form 

 before, either spuriae or migrants, and his original description 

 was based only on the larvae. 



Later, having received specimens of Aphis bakeri Cowen from 

 Prof. C. P. Gillette, I noticed the similarity between these and my 



