330 INSECTS OF MASSACHUSETTS. 



with the hind-wings often crimson, scarlet, or yellow, and traversed 

 by black bands. But as these insects are not particularly interest- 

 ing to the farmer, any further account of them, in this treatise, 

 will be unnecessary. 



3. Geometers. (Geometrce.) 



The caterpillars of the Geometry of Linnaeus, earth-measur- 

 ers, 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 over the ground, 

 step by step, as they proceed. Most of these caterpillars have 

 only ten legs ; namely, six, which are jointed and tapering, under 

 the forepart of the body, and four fleshy proplegs, at the hinder 

 extremity ; the three intermediate pairs of proplegs being want- 

 ing. Consequently, in creeping, they arch up the back while 

 they bring forward the hinder part of the body, and then, resting 

 on their hind-legs, stretch out to their full length, in a straight 

 line, before taking another step with their hind-legs. Some of 

 the Geometers have twelve or fourteen legs ; but the additional 

 proplegs are so short that the caterpillars cannot use them in 

 creeping, and their motions are the same as those that have only 

 ten legs. Some caterpillars with fourteen legs, and wanting only 

 the terminal pair of proplegs, are placed in this tribe on account 

 of the resemblance of their moths to those of the true Geometers. 

 The latter live on trees and bushes, and most of them undergo 

 their transformations upon or in the ground, to reach which, by 

 travelling along the branches and down the stem, would be a long 

 and tedious journey to them, on account of the deficiency of their 

 legs, and the slowness of their gait. But they are not reduced 

 to this necessity ; for they have the power of letting themselves 

 down from any height, by means of a silken thread, which they 

 spin from their mouths while falling. Whenever they are dis- 

 turbed they make use of this faculty, drop suddenly, and hang 

 suspended, till the danger is past, after which they climb up again 

 by the same thread. In order to do this, the span-worm bends 

 back its head and catches hold of the thread above its head with 

 one of the legs of the third, segment, then raising its head it seizes 

 the thread with its jaws and fore-legs, and, by repeating the same 



