COLEOPTERA. HYDROPHILID^. 127 



to the Stems of aquatic plants above the surface ; so that the larvje, 

 when hatched, drop into the water.* The larva of the last-named 

 species (Truncatellus, belonging to the genus Limneblus) is not found 

 in the water ; thus clearly indicating the propriety of the establish- 

 ment of this genus, which Messrs. Solier and Brull6 have so much 

 confused, as well as its relationship with some of the Helophoridae. 



In their perfect state these insects are much less voracious than 

 whilst larvae, the large Hydrophilus piceus chiefly feeding upon 

 aquatic plants, although they also devour with avidity dead larvae and 

 aquatic mollusca. In like manner, M. Miger kept, for several months, 

 specimens of Hydrocharis caraboides, which he entirely fed upon the 

 latter kind of food. This appears, however, not to be their ordinary 

 food, the structure of the jaws, and more especially the internal 

 anatomy, as observed by M. L. Dufour and by Dr. Gaede {Nova 

 Acta, vol. ix. p. 2.), indicating herbivorous habits, the digestive 

 organs differing materially from those of the predacious Dyticidse, 

 and resembling the Lamellicorns. Clairville has informed us, that 

 notwithstanding its large size, Hydrophilus piceus falls an easy prey 

 to the more voracious, but considerably smaller, Dyticus marginalis. 

 When these insects rise to the surface of the water they protrude 

 their antennae, which they again fold back when they descend ; this 

 motion, according to recent observations, is essential for furnishing 

 a supply of air to the spiracles, a bubble being carried by each beneath 

 the thorax, and brought into contact with the organs of respiration. 

 Vide Nitzsch, in Riels Archiv.fur Physiologic, xx. p. 440. ; Burmeister 

 (Shuckard's Engl. edit. p. 392.), and Audouin and BrulU, Hist. Nat. 

 Ins. 



The smaller species, especially the Hydrobii, may often be ob- 

 served creeping slowly along, immediately beneath the surface of the 

 water, with the back downwards, a globule of air, shining like quick- 

 silver, being usually carried between the legs, and which is probably 

 retained by the coating of hairs on the under side of the body which 

 repels the water. During the winter they bury themselves in the mud. 

 The species of this family received from tropical climates prove, as Mr. 



* Lyonnct, Posth. Mem. j), 127. M. De Haan, in his description of the plates, 

 terms tlie insect, represented by Lyonnet (pi. 12. f. 43 — 46.), Elaplirus striatus Fabr. 

 The former word is evidently a misprint for Elophorus, although the insect certainly 

 does not belong to that genus, but rather to Hydrobius. There is, moreover, no 

 palpicorn insect described by Fabricius under the name of striatus. 



