68 DECIDUOUS FRUIT INSECTS AND INSECTICIDES. 
NATURE OF INJURY. 
The larvee upon hatching soon bore into the fleshy hull covering 
the walnut proper. Some individual larve one-fourth grown were 
found feeding in this hull, some burrowing around through the 
fleshy part, and others tunneling back and forth on the inner surface 
next to the walnut shell, producing many little narrow furrows along 
this inner surface. The majority of the larve, however, go at once 
into the nut, entering always through the fibrous tissue connecting 
the halves of the shell at the base or the stem end. The larve may 
bore into the lobes of the kernel or feed on its surface. Some eat over 
a large portion next to the shell, some follow along the central area, 
while others may spend all the time near.the entrance, eating away 
a larger portion of the kernel at this place. In any case the entire ker- 
nel is rendered rancid and unsuited for human consumption. Plate 
VII, figure 1, shows characteristic injury to the walnuts and Plate 
VII, figure 2, a larva at work in the kernel, the latter twice enlarged. 
EXTENT OF INFESTATION. 
Extended search throughout the central part of Contra Costa 
County, Cal., showed the infestation to be general, but light, except 
where trees were near packing sheds, drying grounds, or adjacent to a 
badly infested pear orchard. Many trees were found in such locali- 
ties showing from 5 to 25 per cent of the nuts infested. During the 
winter of 1909-10 small quantities of walnuts were frequently bought 
in the local markets and twice from stands in San Francisco from 
which codling moth larve were secured and which showed the char- 
acteristic injury to the kernel. The writer has also had the same 
experience with walnuts served on hotel and dining-car tables. Mr. 
E. J. Hoddy, of the Bureau of Entomology, has frequently, during 
the past winter, brought in walnuts from various parts of the county 
showing the injury and presence of these larvee. 
VARIETIES ATTACKED. 
All of the soft-shelled French varieties of walnuts are subject to 
infestation, and in fact any of the soft-shelled sorts having a fibrous 
tissue connecting the halves of the shell at base. Moths were reared 
the past season from the Mayette, Concord, Franquette, and Pari- 
slenne varieties. 
SEASONAL HISTORY OF THE CODLING MOTH ON WALNUTS. 
So far all observations indicate that only the later broods of larvee 
attack the walnuts. No walnuts could be found showing early injury, 
that is, before the shell hardened. Assuming that the larval life in 
walnuts is the same in length as in apples and pears, the earliest date 
of infestation would be late August or early September. The Bart- 
