COLEOI'TEUA. 393 



of which is much shorter than the second ; all the joints are 

 entire. 



Those in which the legs are natatory, the first joint of the 

 tarsi is much shorter than the following ones, and the maxillae 

 are entirely corneous, will form our first tribe, that of the 

 Hydrophilii, which embraces the genus 



Hydrophilus, Geoff. 



Linnaeus merely made these Insects a division (the first) of his genus 

 Pytiscus, but their anatomy is essentially different. The alimentary 

 canal of the Hydrophili is very analogous in its contexture and 

 length, which is more than four or five times that of thd body, to 

 that of the Laniellicornes, and only approximates to the same canal 

 of the carnivorous Insects with respect to the biliary vessels. They 

 neither have the natatory bladder nor excrementitious apparatus which 

 characterize the Hydrocanthari. In the females only, this appara- 

 tus is replaced by organs which secrete the matter that is to form 

 the cocoon that encloses the ova, and to produce it their anus is fur- 

 nished with two fusi. Finally, the male organs of generation have 

 the closest affinity with those of the Clavicornes(l), 



In some, where the body ii5 oval, oblong and depressed, or elon- 

 gated and narrow, the thorax scabrous and narrowed posteriorly, the 

 tibiae are slender and furnished with small spurs, and the larsi fili- 

 form, slightly ciliated and terminated by two strong hooksj the 

 antennae — always composed of nine joints — terminate in a slightly 

 perfoliaceous or nearly solid club, almost in the form of a reversed 

 cone, and the extremity of the mandibles is entire, or ends in a sin- 

 gle tooth. They are all very small, swim but seldom or badly, and in- 

 habit stagnant waters, from which they occasionally remove, to 

 conceal themselves under stones or in the earth. They compose the 

 family of the Helophoridea of Leach, a name which reminds us of 

 the genus Elophorus of Fabricius. 



Here the length of the mamillary palpi does not surpass that of the 

 antennae or is even less. The epistoma is entire or without any nota- 

 ble emargination. 



Sometinies the maxillary palpi are terminated by a thicker and oval 

 joint. 



( 1 ) " The conformation and structure of the male organs of generation in the 

 Palpicornes fully justify the position in the entomological series, assigned to 

 them by M. Latreille." — Leon Dufour, Ann. des So. Nat, VI, p. 172. 



Vol. III.— 2 Z 



