238 SHARP EYES 



what she is drilling for. There is a rival drill in the 

 insect field which she is evidently determined to ex- 

 terminate. I have shown her in the act of pouncing 

 upon another wasp -like insect upon the tree -trunk. 

 These two insects are linked in a most strange fashion 

 in the divine plan of Nature. The second insect is the 

 pigeon Tremex (Tremex columba), a borer of no mean 

 accomplishments, though her drill is less than an inch 

 in length. We may see her almost any day in Au- 

 gust, sometimes half a dozen together working upon a 

 single tree. Sooner or later our ichneumon finds this 

 same tree and searches out her enemy ; for the Tremex 

 has laid its eggs within the tree, and its young larvae- 

 are now driving their tunnels through the wood. It is 

 these that the ichneumon is after. She knows that 

 they are within, and her drill is something more than 

 a mere drill, for when once in place she lays an egg 

 through it, and the little grub which hatches from it 

 immediately takes the hint given by its mother. It 

 searches among the burrows within the tree until it 

 finds the Tremex larva, upon which it fastens itself, 

 living upon it as a parasite, and ultimately destroy- 

 ing it. It is an ichneumon -fly instead of a Tremex 

 which emerges from the aperture in the tree bark next 

 summer. 



The mechanism of this ichneumon instrument is too 

 complex for adequate description here. It is composed 

 of three long pieces, which are dovetailed one with aiv 

 other, and glide easily through their entire length, the 

 boring being accomplished by the alternate gouging 

 of the chiselled tips. 



The entire diameter of this shaft is less than the 

 smallest period on this page, and though constructed 



