47 



The eggs of these insects are laid in rinor-like masses about the tw^igs 

 in July. There they remain until the following spring hatches the cater- 

 pillars coiled within them. The caterpillars then proceed to feed upon 

 the young leaves, and when numeroufe completely strip the trees. At sev- 

 eral places in Quebec, square miles of poplar and birch were completely 

 defoliated last summer by the forest caterpillars; and on the Gatineau 

 branch of the Canadian Pacific Railway in Quebec the trains were re- 

 peatedly stopped by the miasses of caterpillars crowding upon the rails 

 which were effectively greased by their crushed bodies. 



Egg Masses of Tent Caterpillars on Maple Trees. 1. Old egg mass. 2. Normal egg mass. 



NATURE'S METHODS OF CONTROL. 



Outbreaks of these caterpillars occur at intervals; during the inter- 

 vening years, owing chiefly to the activity of their natural enemies, they 

 are much less numerous or at times are even almost rare. 



Insect Parasites. — Certain minute four winged insects of the 

 Order H^inenoptera lay their eggs within those of the moths, and the 

 resulting minute larvae, small white grubs, develop within the Tent Cat- 

 erpillar eggs and destroy them. Certain other parasites of the Orders Hy- 

 menoptera and Diptera breed within the Tent Caterpillars and their pu 

 pae, and are most active agents in their control. 



