356 IXSECTS INJURIOUS TO VEGETATION. 



certain insects, which, from the structure of their caterpillars 

 and their manner of creeping, evidently seem to connect this 

 tribe with the Geometers. Some of these caterpillars have 

 the first and sometimes also the second pair of proplegs, under 

 the middle of the body, so short, that they cannot be used in 

 creeping ; others have only twelve or fourteen legs, the first 

 pair of the proplegs, or the second also, being entirely wanting 

 in them. These caterpillars creep with a kind of halting gait, 

 and arch up the middle of the body, more or less, with every 

 step they take, thereby imitating the gait of the true geome- 

 ters or span-worms. To this group belong the army-worms 

 or cotton-worms, which ravage the cotton-fields of the Southern 

 States. They have sixteen legs; but the foremost proplegs 

 are shorter than the rest, and the caterpillars crook their backs 

 in creeping, which has caused them to be mistaken for geome- 

 ters by some writers. The cotton-worm is green, doubly 

 striped with black on the back, and sprinkled with black dots. 

 It growls to the length of an inch and a half, transforms in a 

 kind of web or imperfect cocoon, and becomes an olive-brown 

 moth, called Noctua xylina by Mr. Say. It is found only as 

 far as the cotton plant is cultivated, and never occurs in New 

 England. The twelve-legged caterpillars are sometimes 

 injurious to cultivated vegetables;^ but not enough so, in this 

 country, to have attracted much notice. Their moths are 

 distinguished by golden or silvery spots on their fore wings. 

 The species, with the first and second pairs of proplegs short 

 and rudimentary, feed mostly on the leaves of shrubs and 

 trees; their moths are of large size, with the hind wings often 

 crimson, scarlet, or yellow, and traversed by black bands. But 

 as these insects are not particularly interesting to the farmer, 

 any further account of them, in this treatise, will be unneces- 

 sary. 



3. Geometers. ( Geometrm.) 



The caterpillars of the Geometr.e of Linnaeus, earth- 

 measurers, as the term implies, or geometers, span-worms, and 

 loopers, have received these several names from their peculiar 

 manner of moving, in which they seem to measure or span 



