THEIR RELATION TO PLANTS 65 



drawn out enormously under unfavorable conditions. 

 Thus, if a piece of infested timber is worked up into 

 furniture, a larva which normally matures in two or 

 three years may live for eight or ten years or even 

 longer; and in some cases wainscoting has been found 

 infested, several years after it has been in place, var- 

 nished and polished so as to forbid the idea that some 

 misguided adult oviposited there after the boards 



FIG. 25. Round- head apple borer: a, puncture where egg is laid; 6, same 

 in section; e, hole from which beetle has issued; /, same in section; g, pupa. 



were in position. Some species require the wood in 

 a particular condition to secure their best development, 

 and so a beetle, before laying its egg, may girdle the 

 twig so as to interrupt the flow of sap and then oviposit 

 above the girdled point. Other larvae bore into live 

 twigs and, when ready to transform to the pupal stage, 

 cut through from the inside until only the bark and a 

 mere shred of woody tissue remain. Then the burrow 

 is securely plugged with sawdust and the larva retreats 

 5 



