184 



INSECT TRANSFORMATIONS. 



availing; in raising the loaded glass, except in con- 

 nexion with two favourable circumstances under 

 which the experiment was performed, and which are 

 necessary to be borne in mind to render the opera- 

 tion perfectly credible: — 1st, that the wedge-like 

 form of the caterpillar's head, in connexion with the; 

 peculiar shape of the glass, enabled it to lift it ; — 

 and 2d, that, one side of the glass resting on the 

 table, the insect only bore half the weight of the glass 

 and book. 



Caterpillar of Cossus escaping from under a loaded glass 



A peculiar toughness of external covering some- 

 times supplies the place of this muscular power in 

 caterpillars. A singular instance occurs in the 

 history of a common downy two-winged fly, with 

 grey shoulders and a brown abdomen, {Eristalis 

 tmax, Fabr.). The grub, which is rat-tailed, lives 

 in muddy pools, with the water of which it has some- 

 times been taken up by paper-makers, and, though 

 subjected to the immense pressure of their ma- 



