THE COMMON CABBAGE WORM. 13 
HAND METHODS. 
For the kitchen garden, hand picking is sometimes practiced, 
especially when plants are first set out. It is laborious, although 
effective if the work is carefully conducted. 
CLEAN FARMING AND TRAP CROPS. 
If cooperation in clean methods of farming and in the use of 
arsenicals could be secured by any possibility, much of the loss due 
to the ravages of this pest might be averted. The practice of leaving 
cabbage stalks in the field after the main crop has been harvested is 
reprehensible. All remnants should be gathered and destroyed, with 
the exception of a few left at regular intervals through a field as 
lures to induce the female butterflies to deposit their eggs upon them. 
Such stalks, being useless, should, where feasible, be poisoned freely 
with arsenicals so that the last generation will have no place to 
develop in the fields. 
UTILIZATION OF NATURAL ENEMIES. 
It is matter of common observation, frequently recorded, that two 
parasitic enemies of this species do excellent service in reducing the 
numbers of their host, viz, the cabbage-worm chalcis fly t and an ich- 
neumon fly.2 (See pp. 8-9.) The former issues from the chrysalides 
through minute holes in the dry outer skins. The latter issues from the 
caterpillars and forms masses of yellow cocoons. As soon as these 
cocoons are seen, all caterpillars that can be collected should be gath- 
ered carefully with portions of the leaves to which they are attached 
and transferred to barrels or large boxes, which should be covered 
with wire netting of a mesh which will permit the parasites to emerge 
but will prevent the butterflies from escaping. An ordinary screen 
mesh of 12 to the inch or coarse mosquito netting will answer this 
purpose. In addition, a few holes should be bored into the bottom 
of the barrel or box used for this purpose, small enough to prevent 
the caterpillars from escaping. This will permit rain water to drain 
off which might otherwise drown the insects. 
SUMMARY. 
The importéd cabbage worm is a velvety green caterpillar measur- 
ing about an inch and a fourth when full grown. It is the larva or 
young of a white butterfly. It begins work soon after young plants 
are set out, and in the case of cabbage riddles the outer leaves and 
bores into the heads. As a result entire crops are often lost. 
1 Pteromalus puparum. 2 Apanteles glomeratus. 
