434 SUPPLEMENT 



parts of these insects would seem to contradict, has, neverthe- 

 less, been confirmed by M. Felix Miger, in a Memoir on the 

 Metamorphoses of the Hydrophili, inserted in the 14th Vol. 

 of the Annals of the Museum of Natural History of Paris. 

 He has fed, for more than a month, the H. caraboides with 

 water- snails. He has also seen H. piceus devour, with avi- 

 dity, these same mollusca and aquatic larvae. But he also 

 remarks, according to his own actual observations, that its 

 principal food consists of aquatic plants, which might lead 

 us to believe that it is carnivorous only from circumstances, 

 or rather that it is omnivorous. Its intestinal canal has been 

 opened, which is very long, and it has always been found 

 filled with the debris of vegetable substances. 



In the larvae, on the contrary, the intestines are so short, 

 that they do not exceed in length that of the entire body. 

 The hydrophili, in the perfect state, have an additional attri- 

 bute, which characterizes the herbivorous insects. This is, 

 that they are provided with two very long cceca, which end 

 in the intestinal canal, near the anus, and are folded on them- 

 selves, in a spiral figure, in the cavity of the abdomen. 



The nature and form of the masticatory apparatus also 

 seem to furnish a fresh proof that these coleoptera are her- 

 bivorous. Yet some insects, though herbivorous, are found 

 to be provided with solid jaws, and strongly denticulated. 



Although the hydrophili can live a long time under water, 

 they are, nevertheless, obliged to respire the air from time 

 to time. They bring themselves to the surface of the water, 

 and to arrive there they have only to hold their feet in a state 

 of repose, and suffer themselves to float. Being lighter than 

 the water, they swim above it at once. The hinder part of 

 the body is then applied to the surface of the water, and seen 

 a little above it. They then raise their elytra a little, or 

 lower the end of the abdomen, so that it forms a vacancy 

 between the elytra, and the hinder part of the body, which 



