i >3 
239 . 
HYDROUS PICEUS. 
Order Coleoptera. Fam. Hydrophilidse Leach , Lat. 
Type of the Genus Dytiscus piceus Linn. 
Hydrous Linn. MSS., Leach, Sam . — Hydrophilus DeG., Geof, Fab., 
Oliv., Lat., Marsh., Gyll . — Dytiscus Linn. 
Antennae inserted upon the anterior margin of the eyes at the 
base of the mandibles, shorter than the head, naked, 9 -jointed ; 
basal joint large, bent, slender at its base ; 2nd and 3 following 
slender and cylindric, the 2nd being oblong, the others trans- 
verse ; the Gth and following forming a perfoliated coriaceous 
club, the Gth joint being somewhat cup-shaped, the 7th and 8th 
transverse lunate, produced above, the 9th subtrigonate (6). 
Labrum exserted, naked, very broad and short, being transverse- 
oval (1). 
Mandibles large, bent, acute, notched near the apex, with 3 strong 
emarginate teeth on the inside, pubescent at their base (2). 
Maxillae short terminated by an indexed and dilated articulate 
lobe, ciliated with rigid bristles, 2 smaller lobes on the inside, 
the upper one producing 2 strong curved bristles, the lower one 
ciliated and pubescent. Palpi very long and drooping, 4-jointed, 
basal joint small, 2nd very long, subclavate, 3rd rather shorter 
and slenderer, 4th much shorter elongate-ovate (3). 
Mentum transverse semi-octagonal. Labium thick and rigid, 
formed of 2 lobes uniting in the centre and pubescent at their 
margin. Palpi short, rising from 2 short fixed scapes, triarticu- 
late, basal joint small, 2nd long robust subclavate, 3rd shorter 
slender subfusiform (4). 
Clypeus entire. Head obtuse. Eyes remote globose. Thorax trans- 
verse trigonate emarginate before. Postpectus heeled , terminated in 
a spine at the extremity of the metasternum and extending beyond the 
coxae. Scutellum large, triangular. Elytra broad, convex somewhat 
attenuated to the apex. Wings ample. Legs, anterior the shortest, 
posterior the longest. Tibiae armed with very long spurs. Tarsi all 
5- jointed , 4 first joints very short in the anterior pair, the 5 th long, 
dilated and triangular in the male, producing 2 simple but unequal 
Claws : four posterior Tarsi formed for swimming, compressed, ci- 
liated internally, basal joint short oblique, 2nd long. Claws hooked 
and bifid, with a strong bristle between them (5, fore leg of female ). 
Larvae inhabiting the water. 
Piceus Linn. Faun. Suec. p. 214. n. 764. 
Male. Piceous, smooth, shining. Antennae and palpi ferruginous. 
Elytra with the margin reflecting green and crimson, each with 
4 punctured lines between 2 faint striae, increasing in depth to 
the apex. Tarsi inclining to castaneous, ciliated with ferruginous 
hairs. Female more glossy and olivaceous. 
In the Author's and other Cabinets. 
