444 SUPPLEMENT 



piratory organ, short and fleshy appendages, and which, 

 when these larvae come to the surface of the water to respire, 

 serve to keep their head down, and the body, as it were, sus- 

 pended by its posterior part. They swim with agility. The 

 other larvae, which he calls rampant, are deprived of these 

 appendages, do not swim, and remain constantly on a level 

 with the water. They do not suspend themselves like the 

 first, but turned on the back, they proceed onwards with 

 considerable swiftness, and make horizontal and vermicular 

 movements. Both these sorts of larva undergo their meta- 

 morphoses in the earth. Their nymphs have always two 

 small appendages at the posterior extremity of the body, and 

 some corneous hairs or aigrettes at the anterior edge of the 

 corslet. The lateral tubercles of the body of the larva are 

 very much diversified in their forms and dimensions. But 

 these modifications have not appeared to M. Miger, to be con- 

 nected with any sensible changes in their habits. The hy- 

 drophili, which are essentially swimmers, may proceed from 

 larvae placed in these two divisions. Their females spin 

 the shell or cocoon, of which we have given the description- 

 But the species which swim with difficulty, appertain, in 

 general, to the second division. Their females carry under 

 the body a silky tissue enveloping the eggs. They have fili- 

 form tarsi, less appropriate to the purposes of natation than 

 those of the species of the first, Avith the crotchets of the 

 tarsi entire or scarcely unidenticulated. 



The Elophori differ from Silpha in the antennae ; from 

 dermestes, in the mandibles and jaws; from hydropMlus, in 

 the mandibles, jaws, palpi, and tarsi. 



The Elophori are small insects which live in the water, and 

 usually swim at the surface, where they remain on duck-weed, 

 confervcB^ and other aquatic plants. According to Schrank, 

 they feed on the larvae of other insects, and tlie spoils of frogs. 

 It has been remarked, tliat when this insect is in the water, it 



