220 BARK-BEETLES; ENGRAVER-BEETr.ES. 



made tight, so as to do away with hiding places. In bins that 

 can be made fairly tight, these insects can easily be controlled by 

 the use of bisulphide of carbon. This is poured on the grain, 

 covering it afterwards with canvas or any other similar material 

 to prevent the too rapid escape of the fumes, which, being heavier 

 than air, gradually permeate the entire mass, killing everything 

 in it without causing any injury to the seeds themselves. It is best 

 to do this w^ork after working hours, at all events away from any 

 fire, as the fumes of this chemical are inflammable, and may other- 

 wise kill the insects in a most unexpected, though very effective 

 way. 



Numerous other and similar insects arc often found under 

 the bark of trees, especially that of the pine. All such beetles 

 are very similar in shape, most are highly polished, others are 

 roughly punctured and gray. 



FAMILY SCOLYTIDAE. 



(Bark-bcctlcs, Engraver-beetles) . 



"Engraver-beetles" are so named because they make burrows 

 of more or less regularity between the bark and the sap-wood, 

 as may be seen in the illustration, (Fig. 235), which illus- 

 trates the work of the Hickory-bark Borer, (Scolyfus 4-sf>inosiis 

 Say). Some of these beetles are also called "shot-hole borers,'' 

 from the little round holes with blackened edges which they make 

 in wood and bark ; and still others are called "Ambrosia Beetles." 

 because the insects actually plant the spores of a fungus in the 

 burrows made in solid wood upon which they and their larv?e live. 

 Most of the members of this large family attack forest trees, and 

 those interested in them should read the excellent work of Dr. 

 Packard, already referred to. 



Bark-beetles are mostly small, some almost microscopic, the 

 larger ones rarely exceeding a quarter of an inch in length. Their 

 form is cylindrical, the hind end of the body is frequently very 

 blunt, or even cut off squarely ; the feelers are short ; elbowed or 

 bent in the middle, ending in knobs at the tip ; the tibiae are usu- 



