234 



INJURIOUS AND BENEFICIAL INSECTS OP CALIFORNIA. 



ventral side and the absence of the power of springing when placed 

 on the back. The larva' are enlarged near the head and thus resemble 

 a horseshoe nail. They are wood borers, feeding beneath the bark 

 oc in the solid wood. The common representative of this family 

 is the flat-headed apple-tree borer which occurs throughout the State 

 and country. 



THE OAK TWIG-GIRDLER" 

 Agrilus politus Say 



( Fi{ 



3) 



Description. -The beetle is about [)■ inch long, one fifth as wide 

 and the color varies from metallic bronze to purple or green. The 

 larva is very slender, white or light yellow, distinctly segmented 



with the largest segment near 

 the head. The average length 

 is about 1 inch. 



Life History. — The life his- 

 tory is not well understood, 

 but the eggs are probably laid 



(on the small branches at the 

 » S axil of a leaf or in a fork, as 



& the young 1 a r v a usually 



enters at such points. The 

 burrow is made just beneath 

 the bark, in the form of a 

 regular spiral, and completely 

 girdles the twig, causing that 

 portion above the spiral to 

 die. Pupation takes place 

 near the bottom of the spiral 

 and tin 1 adults begin to issue 

 in April. There is evidently 

 but one brood a year. 



Nature of Work.— The first 

 symptoms appear in the form 

 of numerous dead twigs throughout the tree. If the bark is removed 

 at the base of such twigs and a spiral burrow disclosed, it is the work 

 of this buprestid borer. 



Distribution. — The oak twig-girdler is found throughout the State, 

 specimens having been collected in the southern, middle and northern 

 parts, wherever the host plaids occur, especially the willow. 



Food Plants. — The favorite host is the willow, but the coast live oak 

 ( Quercus agrifolia) is often severely damaged by attacks of the beetle. 

 Other food plants are California buckeye and hazelnut. 



Control. — Pruning out and burning the infested twigs during the 

 fall and winter of the year has been recommended as an effective 

 means of controlling this pest. 



Natural Enemies.— Mr. Leroy Childs records an undetermined 

 hymenopterous parasite attacking the larvae. 



Fig. 223. — The oak twig-girdler, Agrilus 

 politus Say. Adult and larv;e, enlarged twice. 

 Specimens taken at Walnut Creek by Leroy 

 Childs. (Original) 



,3<1 Childs, Leroy, Mo. Bui. Cal. Hort. Coin., Ill, pp. 150-155, 1914. 



