PIERIS II. 



"When at rest tlie larvae lie extended upon the surface of the leaf, generally along 

 one of the ribs or in a depression, and as they retain tlieir green color to maturity 

 they are effectually screened from notice. When mature they are about one inch 

 in length, cylindrical, covered with fine white papillae from each of which is emit- 

 ted a single short hair. The chrysalids are brownish white marked anteriorly b} 

 a few points and short lines of black, and are distinguishable from those of any 

 other genus by angular ridges on tlie back of the wing covers and head. They 

 may be seen attached to fences and buildings near the food plant, or to the jilants 

 themselves. This description will apply either to Oleracea, or Rapae, which in 

 both larval and chrysalis states are extremely alike. And doubtless will be 

 found to apply as well to the same stages of Virgiaicims. 



Fortunately multitudes of these insects are destroyed by small ichneumon-flies 

 which deposit their eggs in the very young larvae. From these proceed grubs 

 which feed upon the substance of the larva, but instinctively avoid any vital 2)art. 

 In due time the larva becomes a chrysalis and shortly after the matured grubs 

 eat their way out and soon become flies, while nothing is left of the chrysalis 

 but the empty shell. 



Until within a few years, Oleracea was considered to be our only eastern spe- 

 cies of this grouji, and although in its larval state somewhat destructive yet was 

 never so much so as to excite alarm. But of late P. Itapae, an European sjiecies, 

 and a pest of that continent, has been introduced, first being seen in the vicinity 

 of Quebec. From probably two or three individuals and from that centre it has 

 rapidly increased, and, year by year, made its way South and West till it swarms 

 in many parts of New York and New Jersey and in Ohio. Already the loss to the 

 cabbage crop alone begins to be estimated at millions of dollars annually, and it is 

 probable that this species will continue to extend its area till it has taken posses- 

 sion of the whole continent east of the Rocky jNIountains. 



