46 



MISC. PUBLICATION 273, U.S. DEPT. OF AGRICULTURE 



TWIG BORERS AND GIRDLERS 



A few bark- and wood-boring insects belonging to the families 

 Buprestidae and Cerambycidae are of some importance as twig 

 borers, or girdlers, in various forest, park, and shade trees (67). 



Beetles of the family Buprestidae lay their eggs on the bark of 

 twigs, and the larvae, referred to as flatheaded borers because 

 of their horseshoe-nail appearance, work under the bark and into 

 the wood, forming nearly flat tunnels filled with boring dust. The 

 larvae are slender and white, without legs, and the enlarged for- 

 ward segment of the body has horny plates on both the top and 

 lower sides. Species that attack the twigs of coniferous trees usu- 

 ally belong to the genus Anthaxia, Chrysophana, Chrysobothris, 

 or Melanophila. Many species of small flatheaded borers mine 

 under the bark and kill the twigs of broadleaved trees. Some of 

 the most striking work of this character is done by species of 

 Agrilus, which make spiral girdles in the twigs of oak, birch, 

 willow, and other broadleaved trees (fig. 18) . Some of the western 

 flatheaded twig borers and girdlers include the following : 



Figure 18. — Spiral twig girdling is characteristic of Agrilus. 



Species Hosts and distribution 



Agrilus angelicus Horn .... Oak. California. 



anxius Gory Birch, poplar, and aspen. Entire West and 



British Columbia. 



arbuti Fisher Madrone. California and Oregon. 



bilineatus (Web.) Oak, chestnut, and beech. Eastern States and 



west into Colorado. 



politics burkei Fisher Alder. California, Oregon, Washington, Nevada 



and Wyoming. 

 politus politus (Say) Willow, and maple. North America. 



