WALNUT APHIDES IN CALIFORNIA. 27 
narrowed and elongated. The antennse are longer than the body, tapering, seven- 
jointed; two basal joints as broad as long, twice the diameter of the following joints; 
third joint longest, slightly thicker towards its base; fourth and fifth joints rather shorter 
than the third, cylindric; two last joints together about equalling the fifth in length; 
the sixth swelled at its tip into a long oval knob, the seventh more slender but not 
capillary, shorter than the sixth; a broad black band at the base of the third and each 
of the following joints. First vein of the fore wings straight and almost transverse; 
second vein bent near its base, running first towards the apex and then turning rather 
abruptly and continuing straight to the inner margin, more than twice as far from the 
first at tip as base; third vein arising from the stigma near its anterior end, and not 
from the rib-vein forward of the stigma, as it does in the aphides generally, except 
those pertaining to this group, its base and its apex about the same distance from the 
second vein that this is from the first, forking rather forward of its middle, strongly 
bent at this point, and from hence to its tip parallel with the third vein or but slightly 
diverging from it, its tip a third nearer that of the third vein than this is to the second; 
second fork nearer the fourth vein at tip than to the first fork, the triangular cell be- 
tween it and the first fork with its three sides equal; fourth vein short and often nearly 
abortive, shorter than the second fork, equally curved through its whole length, its 
tip much nearer that of the rib-vein than that of the second fork; rib-vein very slightly 
diverging from the margin from the base to the stigma, curved from thence to its tip. 
Stigma oval, about twice as long as wide, watery, sometimes tinged with yellowish. A 
variety Jias the stigma dusky at its tip. Another variety (costalis) has the rib-vein 
coal black interrupted with whitish towards the stigma, which is dusky and black at 
each end. 
In a general discussion of this species before his description Fitch 
refers to the minute cornicles characteristic of this and kindred 
species. In his third report on the insects of New York he mentions 
the European walnut aphis and says u European 0. juglandicola of 
Koch" [Chromapliis juglandicola Kalt.] "appears closely related to 
this present species 7 ' [i. e. Callipterus caryellus]. Fitch gave the 
host plant of his species as the hickory. Oestlund (1887) reports it 
in Minnesota from Gary a amara Nutt. Davis (1910) and other Eastern 
writers record it from hickory in the Eastern States. In California 
the normal food plants are the California black walnut (Juglans 
califomica) and hybrids derived from this tree. 
GENERAL APPEARANCE; CHARACTER AND EXTENT OF INJURY. 
In general appearance this aphis is very similar to the American 
walnut aphis (Monellia carysR Monell) and can not be distinguished 
from it except when viewed under the microscope or a powerful hand 
magnifier. Its habits of life and the character and extent of its 
injury are also very similar to those of M. caryx. The writer had 
observed this aphis for several months before he realized that it was a 
distinct species and not a variety of caryse, as he had previously 
supposed. When the sexed forms appeared it was noticed that the 
oviparous female of caryeUa differed markedly from the same form 
of caryx f and this led to a closer scrutiny of the viviparous form 
resulting in the establishment of the points of divergence shown in 
Table VIII. 
