'208 INSECT ARCHITECTURE. 



ing this, the grub first clears away the particles of 

 earth and sand by placing them on its broad trape- 

 zoidal head, and carrying the load in this manner be- 

 yond the area of the excavation. When it gets deeper 

 down, it climbs gradually up to the surface with simi- 

 lar loads by means of the tubercles on its back, above 

 described. This process is a work of considerable 

 time and difficulty, and in carrying its loads, the in- 

 sect has often to rest by the way to recover strength 

 for a renewed exertion. Not unfrequently, it finds 

 the soil so ill adapted to its operations, that it aban- 

 dons the task altogether, and begins anev/ in another 

 situation. When it has succeeded in forming a com- 

 plete den, it fixes itself at the entrance by the hooks 

 of its tubercles, which are admirably adapted for the 

 purpose, forming a fulcrum or support, while the 

 broad plate on the top of the head exactly fits the 

 aperture of the excavation, and is on a level with the 

 soil. In this position, the grub remains immoveable, 

 with jaws expanded, and ready to seize and devour 

 every insect which may wander within its reach, par- 

 ticularly the smaller beetles; and its voracity is so 

 great, that it does not spare even its own species. It 

 precipitates its prey into the excavation, and in case 

 of danger, it retires to the bottom of its den, a cir- 

 cumstance which renders it not a little difficult to 

 discover the grub. The method adopted by the French 

 naturalists was to introduce a straw or pliant twig 

 into the hole, while they dug away, by degrees and 

 with great care, the earth around it, and usually found 

 the grub at the bottom of the cell, resting in a zig- 

 zag position like one of the caterpillars of the geo- 

 metric moths. 



When it is about to undergo its transformation 

 into a pupa, it carefully closes the mouth of the den, 

 and retires to the bottom in security. 



It does not appear that the grub of the genus 



