HABITATIONS OF INSECTS. 445 



insect bores a cylindrical cavity from two to three inches 

 deep, in hard sand which its mandibles alone would be 

 scarcely capable of penetrating, were it not provided with 

 a slightly glutinous liquor which it pours out of its mouth, 

 that, like the vinegar with which Hannibal softened the 

 Alps, acts upon the cement of the sand, and renders the 

 separation of the grains easy to the double pipkaxe with 

 which our little pioneer is furnished. But the most re- 

 markable circumstance is the mode in which it disposes 

 of the excavated materials. Instead of throwing them 

 at random on a heap, it carefully forms them into little 

 oblong pellets, and arranges them round the entrance of 

 the hole so as to form a tunnel, which, when the exca- 

 vation is completed, is often not less than two or three 

 inches in length. For the greater part of its height this 

 tunnel is upright, but towards the top it bends into a 

 curve, always however retaining its cylindrical form. 

 The little masses are so attached to each other in this 

 cylinder, as to leave numerous vacuities between them, 

 which give it the appearance of filagree-work. You will 

 readily divine that the excavated hole is intended for the 

 reception of an egg, but for what purpose the external 

 tunnel is meant is not so apparent. One use, and perhaps 

 the most important, would seem to be to prevent the in- 

 cursions of the artful Ichneumons, Chrysidce, &c. which 

 are ever on the watch to insinuate their parasitic young 

 into the nests of other insects : it may render their access 

 to the nest more difficult; they may dread to enter into 

 so long and dark a defile. I have seen, however, more 

 than once a Chrysis come out of these tunnels. That its 

 use is only temporary, is plain from the circumstance 

 that the insect employs the whole fabric, when its egg is 

 laid and store of food procured, in filling up the remain- 



