336 INSECTS INJURIOUS TO VEGETATION. 



others only at night. Their colors are generally dull, and of 

 some shade of gray or brown, and so extremely alike are they 

 in their markings, that it is very difficnlt to describe them 

 without the aid of figures, which cannot be expected in this 

 treatise. The caterpillars are nearly cylindrical, for the most 

 part naked, though some are hairy, slow in their motions, and 

 generally provided with sixteen legs ; those with fewer legs 

 never want the hindmost pair, and never raise the end of the 

 body when at rest. Some of them make cocoons, but the rest 

 go into the ground to transform. Many of the Noctuas vary 

 more or less from the characters above given, and the tribe 

 seems to admit of being divided into several smaller groups or 

 families, under which their peculiarities might be more dis- 

 tinctly pointed out. Unfortunately the history of most of our 

 moths is still imperfectly known ; and, for this reason, as well 

 as on account of the length to which the foregoing part of this 

 treatise has already extended, I have concluded to suppress a 

 considerable portion of my observations on the owlet-moths 

 and the rest of the Lepidoptera, and shall confine my remarks 

 to a few of the most injurious species in each of the remaining 

 tribes. 



The injury done to vegetation by the caterpillars of the 

 Noctuas, or owlet-moths, is by no means inconsiderable, and 

 sometimes becomes very great and apparent; but most of 

 these insects are concealed from our observation during the 

 day-time, and come out from their retreats to feed only at 

 night. To turn them out of their hiding-places becomes 

 sometimes absolutely necessary, and it is only by dear-bought 

 experience that we learn how to discover them. This is not 

 the case with all ; those of the first family, which I would call 

 Acronyctians (Acronyctad.e*), live exposed on the leaves of 

 trees and shrubs. They have sixteen legs, are cylindrical, and 

 more or less hairy, some of them closely resembling those of 

 the genus Clostera, having a wart or prominence on the top of 

 the fourth and the eleventh rings, and some of them have the 



* From Acronycta, a genus of moths appearing at night-fall, as the name im- 

 plies. 



