REPORT OF THE SOCIETY 89 



SOME BIOLOGIC OBSERVATIONS ON THE BRONZE BIRCH BORER 



AGRILUS ANXIUS GORY. 



By C. B. Hutchings, Assistant Entomologist, Division of Forest Insects, 

 Department of Agriculture, Ottawa, Canada. 



The Bronze Birch Borer is one of the worst enemies of the Birch. Extensive 

 observations made by the Division of Forest Inse^jts of the Entomological 

 Branch, at Ottawa, in different parts of Ontario and Quebec point to the widely 

 spread ravages of this pest in Canada. It has also been reported as operating 

 seriously in many of the Eastern and Middle States of America. Not only are 

 the cultivated birches — those grown under more restricted conditions in pri- 

 vate gardens and parks — subjected to severe attack, but those found in the 

 forest wilds in their natural habit alike fall a ready prey to the Agrilus beetle. 

 In and around Ottawa the various species of this shade tree have been infested 

 for many years. The cut-leaf varieties have suffered the most, although no 

 species appears to have been entirely immune. At the Central Experimental 

 Farm, in the Driveway, and in many of the city gardens handsome large birches 

 are being gradually killed off in this way. During some seasons the attacks 

 are of less severity. This may be due to various agencies, such as weather con- 

 ditions, health of host, parasites and birds. It has been found that a cold de- 

 ferred spring will keep back the development of the larvae and delay the adults 

 coming to the exterior, while a wet summer will tend to increase the vigour of 

 the tree so that its powers of resistance to withstand insect attack are increased. 



The damage is all done in the larval stage and is of such an insidious character 

 that often the presence of the insect cannot be detected until it has become well 

 established within the host. When once a tree is attacked, its fate is sooner or 

 later, a foregone conclusion. One of the first signs of the presence of the borer 

 is the drooping of the topmost branches as if these had been wilted by fire or 

 girdled. Gradually they die off and present a stag-head appearance, while the 

 rest of the tree appears to be healthy, green and vigorous. The attack having 

 begun in the head of the tree, continues on downwards, branch after branch, 

 wilting and dying off in turn as the larvae eat their way into the fresh, succulent 

 bark until the entire trunk and all the under branches have been completely 

 covered by a net work of very intricate tunnellings. 



Unlike many of the important wood borers, such as Cyllene rohiniae on locust, 

 Goes pulcher on hickory, Monochamus marmorator on balsam, Prionoxystus 

 macmurtrei on red oak,all of which indicate their presence by the piles of saw- 

 dust found ejected at their tunnels' entrance, Agrilus anxius exhibits no such 

 index of its presence and except for a very little f rass pushed out early in its career 



