49 



young more than one caterpillar is usually found upon a lead From 

 the very start holes are eaten quite through the leaf, and the larva at 

 first feeds about the margin of these holes. They feed openly as a 

 general thing, with no other concealment than the leaf itself, which is 

 not folded, although Scudder records a single case in which he found 

 them makiug nests upon hop, resembling those made by the caterpillars 

 of P, comma, soon to be described. 



The chrysalis is often suspended from the leaf or stem of the plant 

 upon which the larva has been feeding, but the caterpillar, when about 

 to pupate, also frequently crawls from its food plant and suspends 

 itself upon some neighboring plant or often upon a stalk of grass. 



DIMORPHISM. 



An interesting instauce of dimorphism occurs with this species. The 

 wintering butterflies all belong to one form, which has been called 

 fabriciij but which differs in both sexes and in both the upper and lower 

 aspects of the wing from the other form. The summer brood eventu- 

 ally developing from the eggs laid by these hibernating butterflies is 

 composed exclusively of the other form, which is known as umbrosa. 

 The differentiation is very marked, and the relegation of each form to 

 its distinctive brood is quite constant. The matter becomes more com- 

 plicated farther south, where there are more annual generations, and 

 here there is to a certain extent an overlapping of forms. Thus, in 1882 

 Mr.' Edwards had bred more than twenty batches of insects, mainly 

 from eggs of which he knew the exact parentage, and had raised over 

 500 butterflies. Up to 1878 all of the eggs laid by hibernating fabrieii 

 produced umbrosa. The eggs of the second brood produced 88 percent 

 umbrosa; of the third brood, 55 per cent umbrosa. and of the fourth 

 brood aWfabricii. In the following year the proportions varied only in 

 the second and third broods, which were changed relatively to 83 per 

 cent and 08 per cent. 



NATURAL ENEMIES. 



The fluctuations in the abundance of this species in hop fields and 

 elsewhere are largely due to the fact that it is commonly subject to the 

 attacks of parasites. Moreover, large number of the eggs are destn >y .. 1 

 by spiders and various insects. The eggs are also infested by a minute 

 parasite, Telenomus graptce Howard, a dozen or more of which will some- 

 times issue from a singleegg. The larva' are stung when full grown by 

 Pteromalus vanesscB Harris and ffoplismenus morulas Say. The smaller 

 dark green or golden colored imagoes of the former species issue in 

 numbers from a hole in the side of the chrysalis, and the single Large 

 somber Jloplismenus morulus perfectly decapitates the chrysalis in its 

 escape. 



Remedies. — Hand picking and spraying with an arsenical solution. 

 8907— Xo. 7 4 



