222 INSECTS INJURIOUS TO VEGETATION. 



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 I-^ to 2| inches. 



This butterfly appears in August, and probably also at other 

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

 ance, it is readily distinguished from it by the darker color of the 

 hind-wings and the angular shape of the silvery character on their 

 under-side. This character is very slender, and is sometimes en- 

 tirely wanting. I have raised the ProgneandCommabutterflies from 

 caterpillars which were so much alike, that I am not certain to which 

 of them the following description 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 

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

 changed to chrysalids within twenty-four hours, and were trans- 

 formed to butterflies sixteen days afterwards. At another time a 

 Progne butterfly was obtained from a caterpillar, which I neglect- 

 ed to describe, on the eighteenth of August, the chrysalis state 

 having 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. (Ilesperiadce). 



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 ex- 

 tended horizontally, and the fore-wings somewhat raised, but 

 spreading a little, and not entirely closed, as in other butterflies; 

 some of them, however, have all the wings spread open when at 

 rest, and there are others in which they are all elevated. Not- 

 withstanding this difference in the position of the wings, the Hes- 

 perians all have certain characters in common, by which they are 



