WALNUT APHIDES IN CALIFORNIA. 19 



ANT ATTENDANTS. 



The sweet juices excreted by the European walnut aphis attract 

 large numbers of ants, of which a large black species, Formica sub- 

 sericea Say, is the most abundant. The author is indebted to Mr. 

 Theo. Pergande, of the Bureau of Entomology, Washington, D. C, 

 for the determination of this species. 



THE AMERICAN WALNUT APHIS (Monellia caryae Moftell). 1 



Callipterus 2 caryae Monell, U. S. Geol. & Geog. Survey Bui. 5, No. 1, p. 31, Jan. 22, 

 1879. 



Monellia 3 caryae Gillette, Jour. Econ. Ent., v. 3, No. 4, p. 367, fig. 6, Aug., 1910. 



HISTORY OF THE SPECIES. 



This plant-louse was first collected in Missouri by Mr. J. T. Monell 

 in 1879. His original description is as follows: 



Winged form; general color pale yellow; tips of antennal joints black; legs entirely 

 pale whitish. Antennae a little shorter than the body; seventh joint equal to or 

 one-third longer than the preceding; fifth joint as long as the two following taken 

 together. Nectaries not perceptible. Rostrum not reaching to the middle coxae. 

 Wings hyaline, veins pale; stigma rather short and blunt at the apex. Stigmal vein 

 subobsolete, its course being only traced with difficulty. The distance between the 

 apex of the lower cubital branch and that of the second discoidal equal to about 

 one-half the distance between the apices of the first and second discoidals. Apterous 

 viviparous females and pupae with four rows of tubercles, each mounted with a capitate 

 bristle. 



Leaves of walnut, hickory and pecan. June-July, St. Louis, Mo. 



This aphis has been reported from Illinois (Thomas, 1880; Davis, 

 1910), Nebraska (Williams, 1910), Oregon (Gillette, 1910), and 

 Michigan (Gillette, 1910), and doubtless occurs in America wherever 

 its food plants grow. 



GENERAL DESCRIPTION; CHARACTER AND EXTENT OF INJURY. 



This aphis is about one-sixteenth of an inch long and about one- 

 third as wide and is generally of a pale lemon-yellow color. It 

 occurs on the lower surface of the leaf and on the nutlets of the 

 eastern black walnut tree and crosses derived from it. When infes- 

 tation is severe, the aphides will also be found on the upper surface 

 of the leaves. The species, according to Mr. Monell and other 

 writers, feeds also on hickories and pecan. The character and extent 

 of its injury is altogether similar to that of the European walnut 

 aphis (CJiromapMs juglandicola Kalt.). This plant-louse does not he 

 so flatly appressed to the plant surface as the European species and 

 is much more active, bearing longer legs and antennae in proportion 



1 Mr. J. T. Monell, of the Bureau of Entomology, has kindly identified the specimens sent to him by the 

 author as Monellia caryae Monell. 



2 The genus Callipterus ("beautiful-winged") was erected by Koch (1855). 



3 The genus Monellia was erected by Oestlund (1887), with caryella Fitch as the type species. 



