ABDNDANCE AND INJURIES 

 ABUNDANCE AND INJUEIE8 



137 



As a rule the5 caterpillars of the Mourning Cloak Butter- 

 flies are to be. found only in occasional colonies, so that the 

 damage they do attracts little if any attention. But some- 

 times the weather or other conditions are so favorable to their 



Fig. so. Poplar twig denuded by caterpiUai'S, showing carpet welx 



development that they multiply beyond this normal limit and 

 are to be found in great numbers. At such times serious 

 damage is often done. In this country such local outbreaks 

 of the species have frequently occurred, generally, however, 

 over very limited areas. So far as I can learn the insect has 



