2 BULLETIN 100, U. S. DEPARTMENT OF AGRICULTURE. 
on roots of either the California black walnut straight or on roots of 
one or the other of these two hybrids. When a graft has been made 
and both stock and scion are putting out leaves simultaneously, more 
than one species of aphis will usually occur on the same tree. In 
such a case the two species feed on their own particular host, but the 
migrant forms of either may be found resting on foliage of the oppo- 
site host. The Paradox and Royal hybrids are used in various parts 
of California as shade trees and will furnish a fine grade of wood, 
which will take on a high polish. 
THE EUROPEAN WALNUT APHIS (Chromaphis juglandicola Kaltenbach). 
Lachnus juglandicola Kaltenbach, Monographie der Familien der Pflanzenlause, 
Aachen, 1843. 
Callipterus juglandicola Koch, Die Pflanzenlause Aphiden, Niirnberg, p. 224, 
1857. 
Callipterus juglandicola Passerini, Gli Afidi, Parma, 1860. 
Callipterus juglandis Walker, The Zoologist, ser. 2, v. 5. p. 2000, Feb., 1870. 
Pterocallis juglandicola Buckton, Monograph of the British Aphides, v. 3, London, 
1881, p. 32-34. 
Callipterus juglandicola Schouteden, Mem. Soc. Ent. Belg., v. 12, p. 209-210. 
Chromaphis juglandicola Essig, Mo. Bui. Cal. State Com. Hort., v. 1, no. 5, p. 
190-194, figs. 72-73, April, 1912. 
In 1870 Walker erected the genus CkromapMs and designated 
Callipterus juglandicola Kaltenbach as the type species. Reference 
to this is made by H. F. Wilson in his paper "A Key to the Genera 
and Xotes on the Synonymy of the Tribe Callipterini, Family Aphi- 
didae," Canad. Ent., v. 42, no. 8, p. 253-259, Aug., 1910. 
HISTORY OF THE SPECIES. 
The species was described originally by J. H. Kaltenbach in his 
"Monographie der Familien der Pflanzenlause" as Lachnus juglandi- 
cola. A somewhat free translation of this description is as follows: 
Wingless: Pale yellow, egg-shaped, flat, square, incised, and armed with glandular 
hairs on the margins; legs whitish-yellow, a black spot on the apex of the hind femora. 
Length, \" . 
Winged: Yellow; eyes red; antennae whitish, with black rings; cornicles yellow, 
hardly noticeable; tail lacking. 
This tree louse occurs sporadically in June and July in numbers under the leaves* 
of the walnut tree (Juglans regia). 
Wingless: Antennae shorter than the head and thorax combined, not markedly 
jointed, whitish-yellow. Apex of antennae black, of third joint ringed black. Eyes 
light red; beak short, scarcely reaching to the first coxae. On the dorsum occur two 
longitudinal rows of black spots, which are absent on younger individuals. Cornicles 
and tail lacking. Legs hyaline whitish-yellow; a black spot is found on the upper 
side of the hind femora at their apices. 
Winged: Antennae noticeably shorter than the body, pale, the four major joints 
black at their apices; third joint distally enlarged; sixth joint with a gradually 
l^pering thin apex. The body is yellow; in many cases the black dorsal spots of the 
abdomen are absent; in other cases but two to six are present; cornicles scarcely per- 
