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 Monell). 1 
Callvpterus 2 caryae Monell, U. S. Geol. & Geog. Survey Bui. 5, No. 1, p. 31, Jan. 22, 
1879. 
Monellia* 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 (ChromapTris juglandicola Kalt.). This plant-louse does not lie 
so flatly appressed to the plant surface as the European species and 
is much more active, bearing longer legs and antennas 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. 
