248 



AN ECONOMIC ENTOMOLOGY. 



abundant as the season advances, and late cabbage often suffers 

 seriously in some localities. By all. odds the best remedy is 

 spraying with the arsenites, at the rate of about one pound in 

 one hundred and fifty gallons of water. A great many other 

 remedies have been recommended, and some of them are un- 

 doubtedly useful, but nothing is so satisfactory and cheap as the 

 arsenite, and without gross carelessness there is not the slightest 

 danger in the application. The cabbage heads from within, — 

 that is to say, the leaves unfold from the centre of the head and 

 do not fold together to form it ; therefore, whatever poison is put 

 upon the plant can fall only upon the outer leaves, and not a 

 particle gets into the head itself The -amount used to a single 

 cabbage-plant is so minute that in order really to poison a man it 

 would be necessary for him to eat about a dozen heads, outer 

 leaves and all, and if death then resulted I would be inclined to 

 attribute it rather to the cabbage itself than to the Paris green or 

 other arsenite employed. The larvae succumb to the poison very 

 readily, and by making the appHcation early in the season the 

 later broods may be materially reduced in number. In ordinary 

 farm practice the heads are cut out and shipped, and in prepar- 

 ing the cabbage for food, the outer leaves of these heads are 

 generally taken off by the housewife because more or less bruised 

 or injured, before they are cooked. Chemical analysis has shown 

 that on a head so prepared, within a week after a heavy applica- 

 tion of Paris green, not a trace of arsenic remained. As a matter 

 of fact, the use of Paris green as against the insect is quite 

 common, although litde is said of it, to avoid exciting prejudice, 

 and I have yet to learn of the first case of arsenical poisoning 

 from eating cabbage so treated. From New Jersey southward 

 and westward, one of our native species, P. protodice, becomes 

 more common and assists its imported relative in making havoc 

 among the cabbages, but this also may be easily controlled by the 

 measures above detailed. 



We find flying abundantly in our fields, and more common 

 among clover, a bright, sulphur-yellow butterfly about as large 

 as the P. rapes, with a single black spot on the fore- wings, and a 

 broad black outer margin to both pairs. On the under side the 

 hind wings have a central orange spot, often with a slight silvery 

 tendency. These butterflies belong to the genus Colias, and the 



