94 INSECTS OF ECONOMIC IMPORTANCE 



worms attack; plow land in August and allow it 

 to lie fallow until the following spring; use poison 

 baits of bran, arsenic, paris green, and molasses; 

 hand-pick, etc. 



The imported cabbage-w^orm ^^ (Ponfia rapcc) 

 Order — Lepidoptera 



This is the common white cabbage butterfly pres- 

 ent all over the United States ; it was imported from 

 Europe and first noted in Canada about i860 and in 

 New York about 1868; it feeds on nearly every 

 cruciferous plant. 



The butterflies appear in early spring and lay 

 their eggs on the cabbage leaves ; the eggs hatch in 

 4 to 8 days and the green velvety larvae complete 

 their growth in ten days to two weeks and change 

 to chrysalids; this stage occupies one to two weeks 

 in summer; the pupae of the last brood in the fall 

 remain over winter as such ; there are three or four 

 broods here. The insect has many parasites and 

 diseases that aid in holding it in check. 



Control — Spray the plants with a poison mix- 

 ture before heading is far advanced; 5 pounds of 

 paste arsenate of lead, 5 pounds whale-oil soap and 

 100 gallons of water have given good results; when 

 plants are well headed one may use hellebore. 



The cabbage aphid ^^ {Aphis brassiccu) 

 Order — Hemiptera 



This is a plant-louse imported from Europe. It 

 is covered with a whitish powdery secretion; it in- 

 jures cabbages, cauliflower, turnips, etc. 



In autumn the males and egg-laying females ap- 

 pear and the latter deposit their dark brown eggs 

 in great numbers on the cabbage leaves ; in the early 



10 Chittenden— U. S. Bu. Ent, Circ. 60. 



1^ Herrick and Hungate — Cornell Univ. Expt. Stat., Bull. 300. 



