COLEOPTERA. 
471 
hardens, and becomes Impervious to water. The ova it contains 
are arranged symetrically, and kept in situ by a sort of white 
down. These cocoons float on the water. 
The larva is depressed, blackish and rugose, and has the 
faculty of throwing back its brown, smooth round head. This 
enables it to capture the little Mollusca which navigate the 
surface of the water, its back serving as a point d’appui or 
anvil on which it mashes the shell in order to devour the ani- 
mal it contains. The body of these larvae becomes flabby as soon 
as they are caught. They swim with great facility, and are pro- 
vided with two fleshy appendages beneath the anus Avhich serve 
to maintain them on the surface of the water, head downwards, 
when they come there to respire. According to M. Miger, to 
whom we are indebted for these observations — Ann. du Mus. 
d’Hist. Nat. XIV, 441 — the larvae of other Hydrophilii are de- 
prived of these appendages, and neither swim nor surpend 
themselves like those of which we have been speaking. The 
females of these species swim with difficulty, and cany their ova 
under the abdomen enclosed in a silken web ; but these species 
belong to the last subgenera of this tribe. 
The Hydrophilus proper of Leach consists of species in which 
the tarsi are identical in both sexes, and not dilated, the pectoral 
spine terminates with the post-sternum, and in which the scutel is 
proportionally smaller*. 
In all the following Hydrophilii, the two intei'mediate joints of 
the antennal club are exactly transversal, of a regular form, not pro- 
longed into a tooth at either extremity, and without any space be- 
tween them ; the last is obtuse or rounded at the end. The pectus 
exhibits neither carina nor spine. The tarsi are less, or not at all 
fitted for natation, but slightly or not ciliated, and terminated by 
large, equal, and simple hooks. 
Those in which the maxillary palpi are hardly longer than the 
antennae, with the last joint shorter than the preceding one, and 
cylindrical, in which the body is low, and the elytra are truncated 
at the extremity, or very obtuse, form the genus 
Lijixebius, Leach\. 
Those, in which the maxillary palpi are hardly longer than the 
antennae, with the last joint as long as the preceding one or longer, 
and almost oval, and in which the body is convex, are comprised by 
the same English savant in two genera. In one of them, the 
Hydrobius, Zeac/i, 
The eyes are depressed or but slightly convex ; the anterior extre- 
* To the Hydrous, Leach, besides the piceus,, refer the following species cf 
Fabricius : the ater, olivaceus, rufipes, &c. Those, which the latter calls caraboida, 
tllipHcus, Sec., are Hydrophili properly so called of Leach, 
t H. giifCKS, truncatdlus, Fab. 
