520 



INSECTA. 



First,— Those with very short 10 or 11-jointed antennae, the third and following joints forming a subcylindrical, 

 serrated mass. 



Potamophilus, Germ. (Hydera, Latr.), have the antennae not lodged in cavities, and rather longer than the head, 

 with the first joint nearly as long as all the rest, and the second short and globular ; the palpi are exserted and the 

 mouth is naked. Parnut acuminatus, Fabr. 



Dryops, Oliv., has the antennae shorter than the head, and received in a cavity beneath the eyes, nearly covered by 

 the secondjoint, which is large, dilated, and ear-like ; the palpi are not exserted. Leach applies this generic name to 

 Dryops Dumerilil, which differs from the others (which he names Parnus) in the length of the feet and form of the 

 thorax, &c. 



Second, — Those with filiform 11-jointed antennae, at least as long as the head and thorax. 



Elmis, Lat. (Limnius, 111.), [insects of very small size], found in water, under stones, or the leaves of the water-lily. 



Third, — Those with very short 9 or 6-jointed antennae, terminated in a nearly solid, oval, or globular mass. 



Macronychas, Mull., has five distinct joints in the tarsi, the body oblong and antenna; 6-jointed. M. 4-tubcrcu- 

 latus, Mull. 



Georissus, Latr., has only four distinct joints in the tarsi, the body short and nearly globular, and the antennae 

 9-jointed. Pimelia pygiruea, Fab., [a very minute shining black insect, witli deep rows of dots on the elytra ; 

 rather rare]. 



THE FIFTH FAMILY OF THE COLEOPTERA PENTAMERA,— 



The Palpicornes, — 

 Possesses, like the last, antenna: terminated in a club, which is ordinarily perfoliated, but of not more 

 than nine joints in any species, inserted beneath the lateral and advanced margins of the head ; never 

 longer than it and the maxillary palpi, and often shorter than the last-named organs ; the mentum is 

 large and shield-shaped. The body is generally ovoid, or hemispherical and convex. The feet are in 

 the majority proper for swimming, and have only four or five distinct joints, the basal joint being 

 much shorter than the following ; all the joints are entire. 



Those species which have the feet fitted for swimming, with the basal joint of the tarsi much 

 shorter than the following, and the maxillae entirely corneous, compose a first tribe, Hydrophili, which 



embraces the genus 



Hydrophilus, Geoffroy, — 



Which Linnajus regarded only as a first division of his genus Dytiscus, but the anatomy of the two 



groups differs materially : the digestive canal of the Hydrophili, in its great length and texture, having 



much analogy with that of the Lamellicornes, approaching the carnivorous tribes only in its 



biliary vessels. 



Some of these have the body either oval, oblong, and depressed, or long and narrow, with the thorax rough and 

 narrowed behind; the legs slender ; the tarsi filiform, but slightly ciliated ; the antennae (always 9-jointed) termi- 

 nating in an obconical and nearly solid club. These Palpicornes are all very small; they swim but little and 

 badly, inhabiting stagnant water, which they occasionally quit in order to hide themselves in the earth or under 

 stones. They compose the family Helophoridea of Leach, corresponding with the Fabrician genus Elophorus. 



Elophorus, Fab., having the body oval, thorax transverse, and eyes slightly elevated ; and 



Hydrochus, Germ., having the body long and narrow, the thorax oblong, and the eyes prominent (H. clongatus, 

 Fabr.), have the maxillary palpi terminated by an oval joint ; whilst in 



Ochthebius, Leach, the maxillary palpi are terminated by a more slender, short, and conical joint, and the 

 thorax is nearly semiorbicular. E. pygmaus, Fabr. ; Hydrcena riparia, Latr. 



Hydrcena, Kug., has the maxillary palpi much longer than the head and antennas, with the terminal joint larger 

 than the preceding, fusiform, and pointed at the tip. They have the aspect of Ochthebius. E. minimus, Fab. ; 

 Hydrama riparia, Kugel. 



The other Hydrophiliens have the body ovoid or subhemispherical, and generally convex, with the thorax much 

 broader than long, the tibiae and tarsi generally with long hairs. 'They compose the family Hydrophilidea of 

 Leach, or the genus Hydrophilus, Fabr. 



Spercheus, Fabr., has only six joints in the antennae, and the clypeus is notched. S. emarglnaius, Fabr. [a very 

 rare British species]. 



Globaria, Latr., has the body nearly spherical, laterally compressed, and capable of being rolled into a ball like 

 Agathidium. Its antennae appear to be only 8-jointed, the fifth being dilated internally into a spine, the terminal 

 joints forming a very elongated, nearly cylindrical club, pointed at the tip; the elytra entirely embrace the abdo- 

 men, the four posterior tibiae having a brush of long hairs at the tip. The only species, G. Leachil, is small and 

 exotic: I believe it to be from South America. 



All the remaining Hydrophiliens have nine joints in the antennae, with the club oval or ovoid, and the body not 

 contractile into a ball. 



Hydrophilus, Geoff., comprises the largest species in the tribe, with the two intermediate joints of the club of 

 the antennae obtuse at one end, and elongated, arched, and pointed at the other; the first joint of the club is 



