BURROWS OF THE SCOLYTUS. 147 



the larvae assume the pupal form, and, after under- 

 going their change into the perfect insect, gnaw their 

 way through the bark, and are ready to lay the foun- 

 dations of new colonies. 



When a great number of these insects bore into a 

 tree, they often destroy it entirely, the bark being 

 separated as completely from the wood as turf is 

 severed from the ground when the spade is passed 

 under it. There is a tree or rather, what was a tree 

 standing within a few yards of my house, which 

 has been stripped by the Scolytus. The whole of the 

 bark has peeled off, and nothing is left but the naked 

 wood, scored all over with the radiating tunnels of 

 the destroying insect. 



It is much doubted whether the Scolytus ever 

 attacks a healthy tree, principally, as is conjectured, 

 because in such trees the burrows of the insects are 

 filled with sap, which not only drives out the Beetles, 

 but prevents their eggs from being hatched. Still 

 when a tree becomes unhealthy, the attacks of the 

 Scolytus prevent it from recovering itself; and such 

 serious damage has been done by this insect to our 

 trees, especially the elms in and about London, that 

 the attention of entomologists has long been directed 

 to the subject, in hopes of discovering some device 

 by which the ravages of the Scolytus may be checked, 

 if not altogether stopped. As yet, however, no scheme 

 has succeeded. Various plans have been suggested, 

 such as injecting poisonous fluids into the hole made 

 by the mother Scolytus. This might possibly answer, 

 provided the operater could be sure of discovering all 

 the holes, and provided that the liquid did not kill 



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