CANKER WORMS. 8l 



pots and are attached to the bark, in exposed situations, in masses 

 of from 60 to 200, placed side by side as seen in figure 40, e. 

 The eggs highly magnified, are shown in figure 40 a and 40 h. 



The eggs are deposited in fall or 

 early winter (sometimes in mild 

 winters as late as [March). They 

 hatch about the same time as those 

 of the other species and the larvae 

 act in a similar manner, entering 

 the ground about the same time. 

 Instead of forming- a cell lined with ^. <n c 1. 1 



^ Figure 40— Fall canker "wonn; a. 



silk, however, this species spins a ami ^. egg=', enlarged ; c. segment 



' ^ f f of larva enlarged; e. egg cluster; 



tough cocoon, and the moths come ^- ^"^^ giown larva. 

 forth and begin laying eggs in October and November. 



HOW TO FIGHT CAXKER-WORMS. 



The natural enemies of the canker-worms, including Ichneu- 

 mon, Tachina and Chalcid flies, certain wasps and beetles, and 

 various kinds of birds, are so numerous as to prevent serious 

 damage save in exceptional years. In the absence of these nat- 

 ural enemies, however, or when the weather conditions are spe- 

 cially favorable to the increase of the worms, active measures 

 must be taken to save the trees. 



One of the surest preventive measures is to place a band of 

 tarred paper about the tree in [March and smear it with printers' 

 ink, thus preventing the ascent of the female moths and the 

 deposit of eggs. In case the bark is very rough, it should be 

 scraped smooth to prevent the insects from crawling up behind 

 the paper. The ink must be renewed often enough to prevent 

 hardening, or it will be of no use. If the fall canker-worm is 

 present, of course the treatment must begin in October. If the 

 trees are already attacked, jarring the limbs will cause many of 

 the worms to spin a thread and drop to the ground. If the band 

 of printers' ink is in place they will be unable to return to the 

 attack and may be destroyed. 



The surest way of fighting this pest, however, is by spraying 

 with Paris green or arsenate of lead (Disparene). For this 

 purpose the pump should be powerful enough to develop a pres- 

 sure of at least 60 pounds to the square inch, and all parts should 

 be made of brass and carefully adjusted. The formulas for use 

 6 



