224 THE STUDY OF INSECTS 



trees and shade-trees. Although they attack many kinds of trees, the 

 apple and the elm are their favorite food-plants. 



There are two species of canker-worms which resemble each other to 

 such an extent that they were long confounded; but they differ struc- 

 turally, and they differ also in habits. The two species agree in being 

 loopers or measuring-worms in the larval state, in the possession of ample 

 wings by the adult male, and in the adult female being wingless. They 

 are easily distinguished however, in all stages, the eggs, larvae, and adults 

 differing markedly. 



The fall canker-worm is so called because the greater number of the 

 moths mature in the autumn and emerge from the ground at this season; 

 but a considerable number come out of the ground in the winter during 

 warm weather, and in the spring. As the females are wingless they are 

 forced to climb up the trunks of trees in order to lay their eggs in a 

 place from which the larvae can easily find their food. The eggs appear 

 as if cut off at the top, and have a central puncture and a brown circle 

 near the border of the disk. They are laid side by side in regular rows 

 and compact batches, and are generally exposed. 

 They hatch in the spring at the time the leaves 

 appear; and the larvae mature in about three 

 weeks. In this species there is a pair of ves- 

 tigial prolegs on the fifth abdominal segment. 

 The pupa state is passed beneath the ground in 

 a perfect cccoon of fine densely spun silk. The 

 adult male is represented by Figure 3S6. There 

 is a distinct whitish spot near the apex of the 

 fore wings. The moths of both sexes lack 

 the abdominal spines characteristic of the spring canker-worm. 



The spring canker-worm, Paleacrita vernata. — The eggs are ovoid 

 in shape, and are secreted in irregular masses, usually under loose scales 

 of bark or between the leaflets of the expanding buds. The larvae hatch 

 about the time the leaves expand, and become full-grown in from three 

 to four weeks. They vary greatly in color, and are marked on the back 

 with eight narrow, pale, longitudinal lines which are barely discernible; 

 the two lateral lines of each side are much farther apart than the others; 

 and there are no prolegs on the fifth abdominal segment as in the fall 

 canker-worm. The pupa state is passed below the surface of the ground 

 in a simple earthen cell, which is lined with very few silken threads. The 

 adult moths usually emerge early in the spring before the leaves expand; 

 but they sometimes appear late in the fall, or on warm days during the 

 winter when the ground is thawed. In both sexes the adult of this species 

 is distinguished by the presence of two transverse rows of stiff reddish 

 spines, pointing backwards, on each of the first seven abdominal seg- 

 ments. 



The raspberry geometer, Synchlora tzrdta. — The larva of this species 

 feeds on the fruit and foliage of raspberry, but chiefly on the fruit. It, 

 like some other members of this subfamily, has the curious habit of 

 covering its body by attaching to it bits of vegetable matter, so that it is 

 masked beneath a tiny heap of rubbish. The wings of the adult are of a 

 delicate pale green color crossed by two lines of a lighter shade; the face 

 is green; and the abdomen is not marked with pink and white ocellate 

 spots, as is the case in certain allied species. 



FlG. 386. — Ahopliila pometaria. 



