182 INJURIOUS INSECTS 



burning the cases in winter, the trees can be easily rid of 

 them. If this is done whenever the first few bags are 

 observed, the task of plucking is light; but where it is 

 not so done, the worms will continue to increase, and 

 partly defoliating the tree each year, slowly, but surely, 

 sap its life. 



THE SLUG OF THE PEAR AND CHERRY TREE. 

 (Sdandria cerasi, Peck.) 



In New England, in June and July, there appears upon 

 the leaves of the Pear and Cherry dark-green slimy 

 creatures, so unlike caterpillars in general that they have 

 received the popular name of slug. When grown, they 

 are nearly half an inch ( 9 / 20 ) long; being largest before 

 and tapering behind, they have something of a tadpole 

 appearance; the head is concealed under the fore-part of 

 the body, and they usually have the tail somewhat turned 

 up when at rest. Their color is a dark-blackish or bot- 

 tle-green, and they exude from their skins a slimy matter 

 which forms a shining trail wherever they move. They 

 eat away the pulpy substance of the leaf, completely 

 skeletonizing it; and as there are sometimes as many as 

 twenty or more on a single leaf, they may do much injury 

 by defoliating the tree, and causing leaves to push out 

 from the buds prepared for next season. When present 

 in large numbers, they give off an unpleasant odor, 

 which may be noticed at some distance from the trees. 

 It takes these slugs about twenty-six days to complete 

 their growth, and after their final moult, they no longer 

 have their slug-like appearance, but, as clean yellow 

 caterpillars, leave the trees, and entering the ground for 

 a few inches, form an oval earthen cocoon, in which they 

 become chrysalids, and at the end of sixteen days come 

 out in their perfect state, that of a fly of the order Hy- 



