PIERIS II, 
When at rest the larvae lie extended upon the surface of the leaf, generally along 
one of the ribs or in a depression, and as they retain their 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 by 
a few points and short lines of black, and are distinguishable from those of any 
other genus by angular ridges on the back of the wing covers and head. They 
may be seen attached to fences and buildings near the food plant, or to the plants 
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 Virginiensis. 
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 part. 
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 group, and although in its larval state somewhat destructive yet was 
never so much so as to excite alarm. But of late P. Rapae, an European species, 
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 Bocky Mountains. 
