520 
INSECTA. 
First, — Those with very short 10 or 11-jointed antennae, the third and following joints fojjming a subcylindrical, 
serrated mass. 
Potamophihis, Germ. {Hydera, Latr.l, 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 i 
mouth is naked. Parnus acuminatus, Fabr. ' 
Dry ops, Oliv., has the antennae shorter than the head, and received in a cavity beneath the eyes, nearly covered by ! 
the second joint, which is large, dilated, and ear-like ; the palpi are not exserted. Leach applies this generic name to 
Dryops Dumerilii, which ditfers 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. 
Macronychus, Mull., has five distinct joints in the tarsi, the body oblong and antennae 6-jointed. M. \-tuhercu~ 
lotus, Mull. 
Georissus, Latr., has only four distinct joints in the tarsi, the body short and nearly globular, and the antennae 
9-jointed. Pimelia pygmcea. Fab., [a very minute shining black insect, with deep rows of dots on the elytra ; i 
rather rare]. 
THE FIFTH FAMILY OF THE COLEOPTERA PENTAMERA,-- 
The Palpicornes, — 
Possesses, like the last, antennae terminated in a club, which is ordinarily perfoliated, hut 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 I 
much shorter than the following ; all the joints are entire. 
Those species wLich have the feet fitted for swimming, with the basal joint of the tarsi much |i 
shorter than the following, and the maxillae entirely corneous, compose a first tribe, Hydrophili, which jj 
embraces the genus || 
Hydrophilus, Geoffiroy, — 
Which Linnaeus regarded only as a first division of his genus JDytiscus, but the anatomy of the two I 
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 j 
biliary vessels. j 
Some of these have the body either oval, oblong, and depressed, or long and narrow, with the thorax rough and j 
narrowed behind ; the legs slender ; the tarsi filiform, but slightly ciliated ; the antennae (always 9-jointed) termi- j: 
nating in an obconical and nearly solid club. These Palpicornes are all very small; they swim but little and j, 
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 Elophortis. 
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 (if. elongatus, 
Fabr.), have the maxillary palpi terminated by an oval joint ; whilst in i 
Ochthebius, Leach, the maxillary palpi are terminated by a more slender, short, and conical joint, and the 
thorax is nearly semiorbicular. E. pygmceus, Fabr. ; Hydrcena riparia, Latr. 
Hydrcena, Kug., has the maxillary palpi much longer than the head and antennae, with the terminal joint larger 
than the preceding, fusiform, and pointed at the tip. They have the aspect of Ochthebius. E. minimus. Fab. ; ; 
Hydrcena 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. emarginatus, Fabr. [a very I 
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. Leachii, 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, Geoflf., 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 i 
