RILEY HACKBERRY BUTTERFLIES. 1 97 



larger size of the female, and her less falcate front wings and 

 broader, more rounded hind wings ; but where these characters 

 can not be relied on, as is sometimes the case, the sexes can yet 

 be distinguished by the difference in the impotent front legs, the 

 male having the feet (prsi) and shanks {tibia;) of these legs cov- 

 ered with soft whitish hairs, while in the female they are naked 

 as in the other legs. 



The butterflies begin to appear in the latitude of St. Louis by 

 the middle of June, and by the end of that month the eggs may 

 be found. These eggs (Fig. 3, a, and 4,/) are attached rather 

 slightly to the underside of a leaf, either singly or in small clus- 

 ters not exceeding a dozen. In form they are nearly globular, 

 with very delicate longitudinal ribs, and still finer transverse striae. 

 In hatching, the enclosed larva pushes open the crown, which lifts 

 like a cap. When first hatched this larva is of a uniform yellow, 

 sparsely covered with a few soft hairs, and with a head (Fig. 4, 

 /') which is jet-black and always hornless — thus differing materi- 

 ally from the head subsequently worn. The larvae of this, the first, 

 brood feed for rather less than a month, when they transform 

 and give out the second brood of butterflies during August. These 

 lay eggs again, which in due time hatch. But the second brood 

 of larvae thus hatching, instead of feeding with good appetite as 

 did the first brood, is more lethargic from the start, and develops 

 more slowly. Every worm, after passing through the second or 

 third molt, ceases to eat ; then shrinks in size and stations itself 

 on the underside of a leaf. Here it changes its fresh green color 

 for a dingy grayish-brown (caused by more or less distinct pur- 

 plish marks on a dingy yellow ground), the better to keep in con- 

 formity with that of its dying support, with which, eventually, it 

 falls to the earth, and there hibernates. A heavy snow may cover 

 it many inches deep ; a drenching rain may soak it through and 

 through ; the mercury may sink 22° F. below, or rise So° above 

 zero ; but this little worm is indifferent to all, and sleeps a profound 

 torpid sleep from the first of October till vegetation starts anew the 

 ensuing spring. The weather in St. Louis is often delightfully 

 mild and even warm long after this larva has gone into winter 

 quarters, but nothing short of the animating breath of the vernal 

 year prompts it to renew the activity it lost the fall before. 



In acquiring its winter habit the joints are greatly contracted, 



