316 INSECTS INJURIOUS TO VEGETATION. 



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

 their markings, that it is very difficult'to describe them without 

 the aid of figures, which cannot be expected in this treatise. The 

 caterpillars are nearly cyhndrical, 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 distinctly pointed out. Unfortunately the history of 

 most of our moths is still imperfectly known to me ; and, for this 

 reason, as well as on account of the length to which the forego- 

 ing 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 re-_ 

 marks to a few of the most injurious species in each of the re- 

 maining tribes. 



The injury done to vegetation by the caterpillars of the Noctu- 

 as, 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^*), live exposed 

 on the leaves of trees and shrubs. They have sixteen legs, are cy- 

 lindrical, 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 hair in tufts like Arctians and Liparians. They make tough 

 silken cocoons, in texture almost like stiff brown paper, into 

 which they weave the hairs of their bodies. Their moths have 



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

 plies. 



