LEPIDOPTERA 665 



there is a pair of vestigial prolegs on the fifth abdominal segment. 

 The pupa state is passed beneath the ground in a perfect cocoon of 

 fine densely spun silk. The adult male is 

 represented by Figure 8ig. There is a dis- 

 tinct whitish spot near the apex of the fore 

 wings. The moths of both sexes lack the 

 abdominal spines characteristic of the spring 

 canker-worm. In the fall canker-worm veins 

 Sc -I- Ri and Rs of the hind wings coalesce 

 for a considerable distance along the second 

 fourth of the discal cell; and veins Rs and Mi 

 of the hind wings separate at the apex of the Fig, 819. — Alsophila pom 

 discal cell. etaria. 



Control of canker-worms. — The two spe- 

 cies of canker-worms are sufficiently alike in habits to warrant our 

 combating them by similar methods. The fact that in each the 

 female is wingless and is thus forced to climb up the trunks of trees 

 in order to place her eggs in a suitable place has suggested the method 

 of defence that has been most generally used in the past. This is 

 to place something about the trunks of the trees which will make it 

 impossible for the wingless female to ascend them. Some viscid sub- 

 stance, as tar, printers' ink, or melted rubber, either painted on the 

 trunk of the tree or upon a paper band which is tacked closely about the 

 tree, is the means usually adopted. Many other devices have been 

 recommended. In the use of this method of prevention, operations 

 should be begun in the autimm, even when it is the spring canker- 

 worm that is to be combated; for in this species some of the moths 

 emerge in the fall or during the winter. 



Although the method just described is still the most available one 

 when tall shade-trees are to be protected, it is now rarely used in 

 orchards. Here the spraying of the trees with Paris-green or arsenate 

 of lead soon after the leaves appear is found more practicable. This 

 method has also the advantage of enabling the fruit-grower to reach 

 other important pests, as the codlin-moth, at the same time. 



Subfamily HEMITHEIN^ 

 The Green Geometrids 



As a rule the members of this subfamily are bright green in color ; 

 and as we have but few other geometrids of this color, the subfamily 

 may be well termed the green geometrids. The distinctive structure 

 that characterizes this subfamly is the fact that vein M2 of the hind 

 wings arises much nearer to vein Mi than to vein M3 (Fig. 820). 



This is a comparatively small subfamily, including 1 7 genera and 

 64 species. The following species will serve as an example. 



The raspberry geometer, Synchlora cerdta. — The larva of this spe- 

 cies 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 



