254 INSECTS INJURIOUS TO VEGETATION. 



plants, grows to the length of one inch and three eighths, passes 

 the winter concealed beneath stones, or in the crevices of walls, 

 and makes its cocoon in the spring. 



The caterpillars of all the foregoing Arctians live almost en- 

 tirely upon herbaceous plants ; those which follow (with one 

 exception only), devour the leaves of trees. 'Of the latter, the 

 most common and destructive are the little caterpillars known by 

 the name of fall web-worms, whose large webs, sometimes ex- 

 tending over entire branches with their leaves, may be seen on 

 our native elms, and also on apple and other fruit trees, in the lat- 

 ter part of summer. The eggs, from which these caterpillars 

 proceed, are laid by the parent moth in a cluster upon a leaf near 

 the extremity of a branch ; they are hatched from the last of June 

 till the middle of August, some broods being early and others 

 late, and the young caterpillars immediately begin to provide a 

 sheher for themselves, by covering the upper side of the leaf with 

 a web, which is the result of the united labors of the whole brood. 

 They feed in company beneath this web, devouring only the up- 

 per skin and pulpy portion of the leaf, leaving the veins and lower 

 skin of the leaf untouched. As they increase in size, they enlarge 

 their web, carrying it over the next lower leaves, all the upper 

 and pulpy parts of which are eaten in the same way, and thus they 

 continue to work downwards, till finally the web covers a large 

 portion of the branch, with its dry, brown, and filmy foliage, re- 

 duced to this unseemly condition by these little spoilers. These 

 caterpillars, when fully grown, measure rather more than one inch 

 in length ; their bodies are more slender than those of the other 

 Arctians, and are very thinly clothed with hairs of a grayish color, 

 intermingled with a few which are black. The general color of 

 the body is greenish yellow dotted with black ; there is a broad 

 blackish stripe along the top of the back, and a bright yellow- 

 stripe on each side. The warts, from which the thin bundles of 

 spreading, silky hairs proceed, are black on the back, and rust- 

 yellow or orange on the sides. The head and feet are black. I 

 have not observed the exact length of time required by these 

 insects to come to maturity ; but towards the end of August and 

 during the month of September they leave the trees, disperse, 

 and wander about, eating such plants as happen to lie in their 



