572 THE MONTHLY BULLETIN. 



A NOTE ON THE WESTERN TWIG BORER. 



By Harry S. Smith. 



lu looking up some references in the old series of the Bulletins of 

 the Bureau of Entomology I came across the record of some interesting 

 observations by Mr. Albert Koebele on the insect which is now known 

 in California as the Western Twig Borer, Polycaon confertus Lee. 

 These observations seem to have escaped the attention of entomologists 

 to a large extent, and since this insect has become a pest of considerable 

 importance in California it will no doubt be of value to those interested 

 to familiarize themselves with Koebele 's studies. I am therefore tran- 

 scribing the note herewith. It is found in Bulletin No. 22, Old Series, 

 Division of Entomology, U. S. Department of Agriculture, pages 85-86. 



"THE MADRONA TREE BORER. 



(Polycaon confertus Lee.) 



This destructive beetle occurs to a greater or less extent every spring 

 and summer upon various fruit trees, vines, etc., boring into the fresh 

 wood and destroying it. During my stay in the Santa Cruz Mountains 

 the past summer they were observed everywhere, and most abundantly 

 during May and June. On any dead tree, as soon as the leaves begin 

 to fade, this beetle may be found, though always most abundantly upon 

 the Madrona tree (Arhutus menziesii) . Old trees of this species, such 

 as have been allowed to lay on the ground for a year or two, are always 

 completely perforated with holes from which these beetles have made 

 their exit. In cutting through one finds the wood nothing but mines 

 produced by the larvas, the mines generally running lengthwise, but 

 often crossing each other. The Madrona tree seems to be the ordinary 

 if not the only plant in which the beetle breeds. Notwithstanding that 

 the mature insect bores in almost any kind of fresh wood, and especially 

 favors such as has been somewhat injured by the hot sun, the larva is 

 not, or has never yet been, found in such places. It is the general belief 

 here that it breeds in the wood of oak, yet, so far as my experience goes, 

 its larvse are never found in other than the Madrona wood. It is very 

 remarkable, in view of the above, that they should live and transform 

 within apples from which this beetle has been bred. 



