COLEOPTER A. HVDROPHILID^. 1 23 



into a ball {fig- 8. 5. Hydrocharis caraboides) ; tbc tborax is broader 

 than long ; the edges of the tibia} are but slightly spined, but they 

 are terminated by strong spurs ; and the tarsi, especially those of the 

 posterior legs, are commonly ciliated, so as to be serviceable in swim- 

 ming ; the basal joint is often minute. The mandibles {fig- 8. 8. man- 

 dible of H. piceus) are much toothed on their inner margins ; the 

 antennae {fig- 8. 7. antennae of the same) are clavate, and generally 

 9-jointed * ; and the maxillary palpi are often ver}' much longer than 

 the antenna; ; the outer lobe of the maxilla; is short, broad, and 

 articulated at the base {^fig- 8. y. maxillae of the same). The mentum 

 is transverse, and the labial palpi short {fig. 8. ic). 



The typical insects of this family are amongst the largest of the 

 water-insects ; and it is a curious circumstance that the species found 

 in our country exceed in size those from tropical climates ; many of 

 the species are, however, very minute. This family is more truly 

 aquatic than the preceding, although the species do not swim with 

 that agility which is exhibited by the Dyticidae, paddling along by the 

 assistance of their ciliated posterior legs, which they move alternately, 

 whereby the force of their strokes is weakened ; when swimming, 

 also, their antennae are concealed, and their palpi porrected ; thus dif- 

 fering in both these respects from the Dyticidae : on being taken out 

 of the water, however, they extend their antennae. Their walking 



Erichson, Kafer Brandenburg. 



Sturm. Deutchsl. Fauna, vol. ix. and x. 



Lyonyiet. Posth. Memoirs, vol. i.° 



Miffcr, in Annal. du Museum, vol. xiv. ; and Bull. See. Philom. vol. ii. 



Dufoiir, in Ann. Sc. Nat. 2d series, vol. iii. 



livsel. Ins. Belust. vol. ii. 



Harris. Aurelian ; and the general works of Fabricius, Stephens, Marsham, ^c. 



* Mr. MacLeay considers the antennas to be in reality 11-jointed; the place of 

 the eighth and tenth joint being indicated by tlie'^jecttS intervening between the 

 seventh and eighth, and eighth and ninth, distinct joints. M. Pcrcheron, however 

 {Genera des Insectes, pi. 3.), describes the antenna; as 11-jointed ; the three last joints 

 being soldered together, and forming what has been regarded as the ninth joint. I 

 can see no transverse trace of the articulations as figured by M. Percheron, although 

 the margin of the ninth joint apparently indicates by its impression the existence of 

 three joints soldered together ; but, by carefully examining the antenna; of the va- 

 rious genera of which this and the preceding family are composed, I think it will 

 appear that the loss has taken place among the small central joints at the base of the 

 club. 



