282 INSECT PESTS OF FARM, GARDEN AND ORCHARD 



body is black, thickly covered with streaks and dots of yellowish 

 white; the second segment is without spines, but with a row of 

 yellowish tubercles in their place; the third segment has four 

 branching spines, all black, with a spot of dark yellow at their 

 base; and on the fourth segment are four spines, as there are on all 

 the others, excepting the terminal, which has two pairs, one pos- 

 terior to the other. The spines arc yellow, with blackish branches, 

 excepting the terminal pair, which arc black; and there is a row of 

 reddish ones on each side. The under surface is^yellowish gray, 

 darker on the anterior segments, with a central line of blackish, 

 and many small black dots. 



The chrysalis is ash-brown, with the head deeply notched, and 

 with eight silvery spots on the back; this stage lasts from eleven 

 to fourteen days and the butterflies emerge in July. These lay 

 eggs for another brood late in July and throughout August, mainly 

 upon the hop-plants, where they are to be found. When the cater- 

 pillars of this brood are numerous they sometimes do considerable 

 damage to the foliage, but both this and the following species are 

 ordinarily prevented from becoming overnumerous by several 

 parasites of the eggs and larvse. Only when for some reason con- 

 ditions are unfavorable to the development of its parasites does 

 either species become especially abundant. In fact, Dr. J. B. 

 Smith, who made extensive observations upon hop-insects in 1883. 

 states " that not one in ten of the insects ever attains the butterfly 

 state." 



The chrysalis stage of the second brood is somewhat longer 

 than the first, sometimes lasting twenty-six days, and the butter- 

 flies emerge from the latter part of August until the end of October, 

 and at once seek quarters in which to hibernate over winter. 



Both this species and P. comma are dimorphic, the winter and 

 summer forms differing in both sexes in both the upper and lower 

 aspects of the wings. In the South, where from three to five 

 broods occur in a season, both forms are usually found in the sec- 

 ond and third broods, the summer form, var. umbrosa, gradually 

 decreasing until all of the fourth brood are the hibernating winter 

 form, var. fabricii. 



