GOAT MOTR. 187 



was the famous Cossus, or tree-grub of the Eomans, which was 

 thought so great a delicacy by the ancients, I cannot believe that 

 any palate could have attained so very artificial a condition as to 

 endure this repulsive creature, much less to consider it as a dainty. 



It grows with wonderful rapidity, being when it has reached 

 its full size seventy-two thousand times heavier than when it 

 was hatched ; its segments are deeply marked, and in colour it 

 is of a mahogany-red above, and yellowish below. The whole 

 surface is smooth and polished, and, as may be presumed, con- 

 sidering the life which it leads, its muscular strength is enormous. 

 Not only are the large and trenchant jaws extremely thick and 

 strong, but the development of muscle is singvdarly great ; and 

 the head is of a wedge-like shape, so that the creature can force 

 itself even through hard wood. It feeds entirely upon the 

 substance of the tree in which it takes up its residence, and 

 leaves in its tunnels a considerable amount of dibris. As the 

 creature increases in size, its tunnel increases in diameter ; and 

 it is an amusing task to cut up an old and soft-wooded tree, and 

 follow the caterpillar through its manifold windings. 



It lives for some three years in the larval condition, and 

 during the winter it lies dormant in an ingeniously made cocoon, 

 constructed from wood-chips and silken thread, a large store of 

 which can be produced by this caterpillar. Several cocoons are 

 now before me, which I took from a willow tree in Erith marshes. 

 Out of a great number of specimens I have selected four, in 

 order to show the different dimensions of the cocoons. The 

 largest is two inches and a quarter in length, and rather more 

 than an inch in width. In shape it is nearly cylindrical, except 

 at the ends, which are rounded. One of them is intact, but the 

 other has a round hole through which the larva has emerged. 

 It is composed of wood-chips of various sizes, looking like 

 ordinary sawdust, which are loosely, though thickly, fastened 

 upon a silken framework. Near one end of the cocoon the 

 chips are veiy heavily massed, for what purpose seems doubtful. 

 Hough, however, as is the exterior of the cocoon, the inside is 

 quite smooth and soft, not unlike the interior of the tube made 

 by the trapdoor spider. 



The smallest cocoon is barely an inch in length, and is made 

 of much smaller chips, fastened together so strongly that the 

 cocoon retains its cylindrical form when handled, whereas the 



