2 54 Annals Entomological Society of America [Vol.1, 



The Barberry Plant-louse (Rhopalosiphum berberidis Kaltenbach) 



Rhopalosiphum berberidis Kalt. was first noted and described 

 as new in this country in 185 1 by Asa Fitch, in his "Catalogue 

 of the Homoptera of New York." He later gave the complete 

 life history of the species, under the name of Aphis berberidis 

 Kalt., in the "Tenth Report of the Insects of New York." It 

 has also been mentioned in the writings of Walsh, Thomas, 

 Oestlund, and Hunter, but has never been reported outside of 

 New York. 



Mr. J. T. Monell has kindly sent me specimens of this species, 

 collected by him in St. Louis, Mo., and I have frequently found it 

 in Illinois. Mr. Paul Hayhurst writes that he has found it com- 

 mon in Massachusetts. 



Fitch reported it from Berberis vulgaris, this being likewise 

 the only known food plant in Illinois. In Europe it was found 

 by Kaltenbach on Berberis vulgaris, and by Buckton on B. 

 communis. 



I first found this aphid at Urbana, 111., about the middle of 

 June, 1907, on the stems and on the undersides of the leaves of 

 Berberis. It continued to be very abundant until about the 

 first of August, when it became comparatively scarce, although 

 at no time during the entire summer were the plants free from 

 this aphid. During October they again became numerous, and 

 November 14 I found the sexual forms, although at this time 

 most of them were immature. On this date, eggs also were 

 found, these being deposited in the crevices of the bark and in 

 the grooves between the buds and stem. 



This spring (1908) I first examined these plants March 18, 

 and on that date found the eggs all hatched and the reddish-brown 

 immattire stem-mothers numerous upon the stems, although the 

 buds had not yet opened. Eggs of a number of other aphids 

 were observed this spring, but those on the Berberis w^ere the first 

 to hatch, the eggs of the other species not hatching until about a 

 week later. 



Adult stem-mothers were first noticed March 25, and the first 

 winged adults of the second generation eight days later, April 2. 

 Although most of the second generation became winged, many 

 were wingless upon becoming adult. The immature individuals, 

 as well as the adults of this first generation dift'er in coloration 

 from the immature and adults of the succeeding generations, 

 as will be seen from the following descriptions 



