THE COLEOPTERA 147 



many in grooves of tho tunnel. The larvse, on hatching, excavate tun- 

 nels for themselves, leading away from the egg tunnel (Fig. 143) and 

 becoming larger with the growth of the larvae. Pupation is at the end 

 of the larval tunnel in a somewhat wider portion and after transforma- 

 tion the adult bores its way to the outside. In the case of the Ambrosia- 

 beetles a fungus used as food by the insects, grows on the walls of the 

 tunnels and generally turns these walls black. 



Destruction by these insects is mainly of forest and shade trees. As 

 nearly all the bark-beetles appear to prefer dying bark in which to live, 

 the refuse of cutting operations, commonly termed "slash," will provide 

 much of this, and most of the insects will work there. When slash comes 

 to an end, however, by operations ceasing in that area, the increased 

 abundance of the insects due to abundant slash often forces them for 

 lack of other material, to turn to the healthy trees, themselves changing 

 thereby from "secondary" to "primary" foes. Slash should therefore 

 be destroyed before beetles in it can develop to the adult condition. Fire 

 in forests produces many dead and weakened trees also, frequently lead- 

 ing to insect attacks, and epidemics, either local or quite widespread, 

 may thus result. Many trees when the beetles bore into them, pour 

 out their sap or resin, and some of the insects may easily be 

 drowned in this. If attacked by multitudes, however, the supply of 

 sap becomes so reduced that the insects coming later can accomplish 

 their purpose. 



Removing "beetle trees" before the adults escape, and either remov- 

 ing and burning the bark, floating the logs, or sawing the same winter and 

 burning the slabs and trimmings, are some of the measures used for the 

 protection of our forests against these insects. 



One species of Ipid, the Clover Root-borer, tunnels in the main 

 roots of clover. Several other species attack fruit trees, usually those 

 not healthy. 



The Fruit-tree Bark-beetle or Shot-hole Borer (Eccoptogaster rugu- 

 losiis Ratz.). — This European fruit-tree pest has now been in the United 

 States about 50 years and is present nearly everywhere east of and in 

 many localities west of the Mississippi River, and has been reported from 

 California. It breeds in most of the cultivated deciduous fruit trees 

 as well as in several kinds of wild ones. The beetle (Fig. 144) is about 

 a tenth of an inch long, almost black, except the tips of the elytra and the 

 legs, which are dull red. 



In the spring the beetles enter the trees and dig out egg channels one or 

 two inches long, about parallel to the grain of the wood, partly in this, 

 partly in the inner bark. Here, in little niches or hollows along the sides, 

 the eggs are laid. These hatch in a few days and the grubs burrow, 

 first directly away from the egg channel, then turning in various directions, 

 extend these larval tunnel sseveral inches, and pupate at their ends. 



