The Bronze Birch Borer. 145 



turnings and zigzaggings of the burrow as it extended along and around 

 the branch. Eight times the borer tunneled its way through the wood 

 to the center of the branch or farther, once working along for about 

 four inches near the center. This burrow, the work of a single borer, 

 measured a little over five feet in length, and it was evidently all made 

 between June ist and October ist. Surely this is a remarkable piece of 

 work and must have kept the little creature chewing nearly every moment 

 of the four months. 



Oftentimes on the trunk and larger branches the burrows of several 

 borers zigzag across each other in interminable confusion, as shown at a 

 in Fig. 36. Yet it is a remarkable fact that even in this case where the 

 infestation was very severe, there were no indications on the bark of the 

 trunk of any injury beneath, or that the tree was infested by a borer; 

 this fact is well shown in Fig. 33, where small portions of the bark were 

 removed and the numerous burrows of the borer revealed. The burrows 

 mostly extend through the growing wood just beneath the bark, and 

 often the effort of the tree to repair the injury results in a woody growth 

 over the burrow that causes corresponding ridges to appear on the bark 

 (Fig. 30, b). Sometimes a burrow can be traced for several inches by 

 these ridges on the bark. The next year's growth of the tree may cover 

 an old burrow with wood, and burrows have been found thus buried 

 under three annual rings of woody growth, showing that the tree might 

 overcome some of the injury were it not for renewed attacks by the 

 pest. Sometimes the burrowing of the borers weakens the limbs to such 

 an extent that they break from their own weight. 



Historical Notes 



Scientific name. — The first record in the literature of this Bronze Birch Borer 

 concerned its scientific name. Like many other American insect pests, this borer 

 was also named in Europe. One of the adults or beetles found its way into the 

 collection of Dejean, a Frenchman, who published lists of the beetles he had. In 

 the third edition of his Catalogue dcs Colcop feres (p. 63) issued in 1836, he listed 

 this birch borer, giving it the name of Agrilus anxius. But the honor of naming the 

 insect is now credited to Gory, another Frenchman, who first published in 1841 a 

 description of it and courteously used Dej can's name (Hist. Nat. des Coleopteres, 

 Monog. des Buprestides, Vol. 4, p. 226). Dejean recorded the insect from Boreal 

 America. 



In iS.SQ, the insect was first recorded in Ainerican literature by Le Conte, and 

 was then described imder two dififerent names as Agrilus gravis, from Lake Superior 

 and New York, and .Igrilits torfidiis from Lake Superior and Illinois (Trans. Am. 

 Phil. Soc., XI, p. 247) ; he recorded Agrilus anxius from Massachusetts. The 

 former names fell as synonyms of Gory's earlier name of anxius when Dr. Horn 

 monographed the genus Agrilus in 1891 (Trans. Am. Ent. Soc., XVIII, p. 277-366) 



Early economic records. — Dr. Lintner was the first to record anything about the 

 habits of the insect. In 1883, he collected 62 of the beetles " which were observed 

 alighting from their flight in the bright sunshine, and running actively in jerking 



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