468 INSECT A. 



four very distinct joints, or of five, the first 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 HYDROPIIILII, which 

 embraces the genus 



HYDROPHILUS, Geoff. 



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

 Dytiscus* 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 the body, to 

 that of the Lamellicornes, 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 *. 



In some, where the body is 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 tarsi fili- 

 form, slightly ciliated and terminated by two strong hooks ; the an- 

 tennae always composed of nine joints terminated 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 

 inhabit stagnant waters, from which they occasionally remove, to 

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

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

 genus Elophorus of Fabricius. 



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

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

 ble emargination. 



Sometimes the maxillary palpi are terminated by a thicker and 

 oval joint. 



ELOPHORUS, Fab. SILPHA, L. DERMESTES, Geoff. HYDROPHILUS, 



De Geer, 



.The body oval, and the thorax transversal; the eyes but slightly 

 prominent f. 



HYDROCHUS, Germ. ELOPHORUS, Fab. 

 The Hydrochi are only distinguished from the preceding subgenus 



* "The conformation and structure of the male organs of generation in the Pal- 

 picornes fully justify the position in the entomological series, assigned to them by 

 M. Latreille." Leon Dufour, Ann. des Sc. Nat., VI, p. 172. 



f The Elophori of Fabricius, those species excepted which belong to the following 

 subgenera. 



