No. 4.] INSECTS AND GARDEN CROPS. 



325 



the head of a pin, pale yellow at first, but darker after a few 

 days. They hatch in about a week, and the little caterpillars 

 which come from them at once begin to feed on the leaves. 

 At first pale yellow, the caterpillar as it grows becomes vel- 

 vety green, and when full grown is more than an inch long. 



Fig. 2. — Imported cabbage worm butterfly: male and female. 



It now crawls to some protected place, where it changes to 

 the chrysalis form, — the same as that in which the winter 

 is passed, — and becomes quiet while the internal organs of 

 the caterpillar are being built over into those of the adult 

 butterfly. When these changes have been completed the 

 chrysalis bursts open and the adult butterfly appears, and 

 egg-laying for another brood of caterpillars now begins. 

 During the year there are three broods of these insects in 

 Massachusetts, the winter being passed in the chrysalis stage. 



Treat7iient. 



Several methods may be used for control- 

 ling this insect. Hot water applied at about 

 130° will kill the caterpillars usually without 

 injuring the plants, but the disadvantage of 

 this treatment upon a large scale is evident. 



Probably the best method to use is that 

 of spraying with Paris green or arsenate of 

 lead, as these poisons are very destructive 

 to the caterpillars and without danger to the 

 consumer, unless the spraying be done with 

 extreme carelessness and shortly before the 

 heads are cut. There are several reasons why this treat- 

 ment is not dangerous. The head of the cabbage forms from 

 within, only the very outermost loaves being at any time 

 exposed to the poison, and these are removed in trimming 

 the head for market. Then, too, the poison is chiefly needed 



Fio. ;i.— Imixiitcdoiil)- 

 bnnc worm : a, fuU- 

 ^rowii caterpillar; b, 

 chrysalis. 



