242 INSECTS INJURIOUS TO VEGETATION. 



two black spots before the middle, and a row of small orange- 

 colored spots before the hind margin ; tails and posterior edges 

 of the wings powdered with reddish white ; under side gray, 

 with fine blackish streaks, and an angular silvery character 

 somewhat in the form of the letter L on the middle of the 

 hind wings. Expands from 1| to 2| inches. 



This butterfly appears in August, and probably also at other 

 times. Though very much like the preceding in general ap- 

 pearance, it is readily distinguished from it by the darker color 

 of the hind wings and the angular shape of the silvery char- 

 acter on their under side. This character is very slender, and 

 is sometimes entirely wanting. I have raised the Progne and 

 Comma butterflies from caterpillars which were so much alike, 

 that I am not certain to which of them the following descrip- 

 tion belongs. These caterpillars were found on the American 

 elm in August; they were pale yellow, with a reddish colored 

 head, white branching spines tipped with black, and a row of 

 four rusty spots on each side of the body. They were sus- 

 pended on the twenty-first and twenty-second of August, 

 changed to chrysalids within twenty-four hours, and were 

 transformed to butterflies sixteen days afterwards. At another 

 time a Progne butterfly was obtained from a caterpillar, which 

 I neglected to describe, on the eighteenth of August, the chry- 

 salis state haying continued only eleven days. The chrysalis 

 is brownish gray, with silvery spots on the back, a short, thick, 

 and rounded nose-like prominence on the thorax, and the two 

 conical double-pointed horns or ears on the head, the outer 

 points very short, and the inner ones longer and curving 

 inwards. 



2. Skippers. [HesperiadtB.) 



The butterflies of this tribe frequent grassy places, and low 

 bushes and thickets, flying but a short distance at a time, with 

 a jerking motion, whence they are called skippers by English 

 writers. When they alight, they usually keep the hind wings 

 extended horizontally, and the fore wings somewhat raised, but 

 spreading a little, and not entirely closed, as in other butter- 

 flies; some of them, however, have all the wings spread open 



