December, ’18] DAVIDSON: CALIFORNIA PISTOL CASE BEARER 
447 
Distribution 
The insect appears to be confined to the San Francisco Bay region 
and to the counties of Santa Clara, Santa Cruz, Contra Costa, San 
Mateo and Alameda. In the Santa Clara Valley the species is at 
times quite abundant. In the San Ramon Valley in Contra Costa 
County it appears to be quite rare and has perhaps only been recently 
established. 
Food Plants 
These include plum, prune, cherry, apricot and apple. Decided 
preference is given to cherry, and plums (including prunes) of the 
European type. 
Injury 
Injury is caused by the larvae only. Instances in which it has been 
damaging are few. The young larvae from June to September skeleton¬ 
ize the foliage, feeding at first as leaf-miners. Old larvae from late 
February to May attack leaf buds, fruit buds, flowers, foliage and 
occasionally the young fruit. When the larvae are abundant they 
may destroy an appreciable number of fruit buds and blossoms, but 
in general, cherries and plums blossom so profusely that the buds and 
flowers destroyed by the case-bearers are a negligible quantity. Small 
brown scars are formed on the fruit. 
General Biology 
There is one generation a year. The adult moths emerge in May 
and June; the female after copulation deposits her eggs on the leaves 
of the food-plants. The eggs hatch after an interval of 26 days, the 
maximum date of hatching being about July 1. The young larva 
sets about constructing its “case” and once built this is never cast off 
but gradually enlarged as the larva inside grows. In their first instar 
the larvae feed on the soft inner tissues of the leaf and skeletonize it. 
They feed thus until September and then proceed to the twigs and 
limbs to hibernate. Hibernation proceeds through the month of 
September, the larva fastening its case to the bark surface with a silken 
button. About the time when the buds are swelling in spring the 
larvae resume active life and move to the young growth, feeding first 
upon the opening buds and later on the young leaves and fruit. When 
full grown they fasten their case to the leaf surface and pupate. Pupa- 
tion occurs in April and May and after a lapse of 25 days the adult 
moths split apart the valve-like butt of the “pistol” and issue. From 
measurements taken periodically it appears that the larvae molt once 
in the fall and twice in the spring previous to the pupal molt. Just 
