1864.] BOWLES ON PIERIS RAP.^ IX CANADA. 261 



parts of the United States. And tliat it will in the course of time 

 spread over these regions, admits of no doubt. The food-plants of 

 the species are cultivated in every partof the country, and besides, 

 the insect has the power of accommodating itself to altered cir- 

 cumstances. Mr. Curtis, in the worK before mentioned, states 

 that the caterpillars have been found feeding on the willow, and 

 on mignionette, nasturtiums, &c. It is therefore probable that its 

 progress westward will not be impeded by the scarcity of its fa- 

 vorite food in certain localities, but that it will overcome all diffi- 

 culties of this nature by resorting to other plants, not confining 

 itself to the crucifer^e. 



Last autumn, in the vicinity of Quebec, the ravages of these 

 larva) were very great. Large plots, and even fields of cabbages, 

 cauliflowers, &c., were completely destroyed ; the caterpillars only 

 rejecting the strong supporting ribs of the leaves. Serious loss 

 was thus occasioned to market gardeners and others. One inform- 

 ed me that he had sustained a loss of more than two hundred dollars 

 by their depredations ; another that nearly the whole of his crop 

 of cabbages was destroyed, the small portion saved requiring to be 

 carefully washed before being sent to market. A gentleman also told 

 me that they had not only eaten up his garden produce, but had 

 demolished a bed of mignionette, even to the stalks. 



Nature has provided more than one means of checking the in- 

 crease of the species. The chrysalis is attacked by a parasite, 

 (probably one of the Ichneumonidas) as several collected by me 

 this spring gave evidence. Large numbers of the pupa3 are also 

 killed by the frost, where they have been placed in exposed situa- 

 tions, and thus the spring brood of butterflies is materially les- 

 sened. I noticed a sini^^ular circumstance connected with these 

 winter pupje. Living chrysalids, brought into the warm house 

 from the cold outside, invariably shrivelled and dried in a few 

 days. Out of many that I gathered during last winter, not one 

 produced a butterfly. 



Last year the species was exceedingly abundant in the neigh- 

 borhood of Quebec, flying by hundreds over the fields and gar- 

 dens, and even in the most crowded parts of the city ; and this 

 season it promises to be equally numerous. Early in March, the 

 butterflies began to appear in houses, from pupa which had been 

 suspended on the walls during the previous autumn. On the 6th 

 April, at Laval, about fifteen miles trom Quebec, several specimens 

 ■were taken in the open air ; and on the 26th May, I counted more 



