342 REPOKT OP STATE BOARD OF HORTICULTURE. 



common name for the beetles — "shot-hole boilers." Fig. 1, shows the 

 appearance of a twig, natural size, infested with these beetles; and the 

 holes and shriveling- of the bark can be seen fairly well. 



The first holes are made by the adult beetles that eat directly through 

 the bark until they reach the wood, then they tunnel between the bark and 

 the wood, making a hole from an inch to an inch and a half in length, and 

 slightly larger than the insect. This burrow is almost invariably in the 

 direction of the long axis of the limb or very slightly oblique, and is made 

 in the cambium layer, including a little of the wood on the one side and a 

 little of the bark on the other. As the females make this burrow, which is 

 known as the brood chamber, they deposit their eggs to the right and left 

 along its course. The minute grubs hatching from these eggs eat little tun- 

 nels or side galleries at right angles to the brood chamber, likewise keeping 

 in the cambium layer and including a little of the wood and a little of the 

 bark. As they increase in size they make the Ixxrrows larger in diameter 

 accordingly, and soon begin to turn the tunnels in the direction of the long 

 axis of the limb and parallel to the brood chamber. These side galleries 

 are lengthened as the larvse feed until they are about as long as the brood 

 chamber, or possibly longer, by which time the grubs have become full 

 grown larvse. They are small, white, footless grubs with brown heads, one 

 of which is represented magnified in Fig. 2, d. They then eat a little deeper 

 into the wood and thus make a small chamber, known as the pupal chamber, 

 stopping up the entrance with pieces of wood, and there change to pupas. A 

 pupa is represented magnified in Fig. 2, c. 



When the adult beetles ejnerge they simply eat through the bark to the 

 exterior and escape. Thus it is that the limb becomes so full of the small 

 holes through the bark : and as each female deposits about eighty eggs, as 

 can be readily determined by counting the side galleries of the brood 

 chambers, one can readily imagine the result when the adults emerge. 

 From a short section of a small limb, one-half of which is photographed in 

 Fig. 1, there emerged in the laboratory one hundred and sixty-seven adult 

 beetles of one brood. 



As the great bulk of the young beetles soon attack the same tree from 

 which they emerged, and eat holes through the bark, and burrow in order 

 to deposit their eggs for another brood, it can readily be understood that it 

 does not require much time before these insects have completely under- 

 mined the bark, and, by destroying the cambium layer, have killed the 

 limb above the infested place. 



By removing the bark from an infested limb one can readily see the 

 shape of the burrows engraved upon the wood and upon the bark, and, 

 where the limb is badly infested, one will find the galleries so close together 

 and so interwoven that it is difficult to trace the work of a single family. 

 Fig. 3 shows an enlarged picture of such a limb with the bark removed. 



In Missouri this beetle has sometimes three and sometimes four broods 

 during a season, each brood requiring on an average five weeks for its 

 completion; but as the beetles do not all emerge at once, and vary consid- 

 erably in a single tree, the result is the different broods tend to overlap 

 somewhat, and we have found it very difficult to exactly trace the broods for 



