531 . 
HYGROTUS DECORATUS. 
Order Coleoptera. Fam. Dyticidae. 
Type of the Genus, Dytiscus insequalis, Fab. 
Hygrotus Step., Curt. — Hyphydrus Mull., Gyl. — Dytiscus Fab., 
Payk., Panz. 
Antennce inserted in a cavity close to the eyes, as long as the 
head and thorax, filiform, 11-jointed, 2 first joints oblong, the 
basal one curved at its insertion, 3rd and 4th short, 5th nearly 
as long as the 2nd and stouter, the remainder of the same size 
and shape, the last being as long as the 2nd and ovate-conic (6). 
Labrum transverse-elliptic, ciliated and slightly curved in the 
middle, but not notched (1). 
Mandibles convex, truncated obliquely, the angles forming ob- 
tuse teeth, with one on the inside, the teeth much more deve- 
loped in one (2 a), than in the other ( b ). 
Maxillae small, forming a horny claw, with a bundle of strong 
bristles on the inside towards the base, and a few near the 
apex : Palpi, internal long slender and biarticulate, the basal 
joint short, external clavate, 4-jointed, 2 first joints small, 3rd a 
little larger, 4th very large subfusiform (3) . 
Mentum transverse, bilobed, swelling a little at the centre. 
Palpi short, triarticulate, 2 first joints subquadrate, 3rd larger 
subreniform (4). 
Head large, broad at the base, convex before : eyes lateral and ovate * 
Thorax considerably broader than the head at the base, very short , 
forming a narrow band, concave before : scutellum invisible. Ab- 
domen convex beneath. Elytra ovate, very convex, truncated at the 
base, broadest before the middle, and subconical at the apex. Wings 
ample. Legs, 4 anterior short , posterior formed for swimming: Tibiae, 
4 anterior furnished with a series of bristles and ciliated with long 
hairs outside towards the apex : tarsi 4 anterior 4- jointed , cushioned 
beneath and a little dilated in the males, ls£ and 2nd joints some- 
what obtrigonate, 3rd rather elongate and bilobed at the apex, 4th 
the smallest : claws 2 (5) posterior tibiae ciliated on the inside, 
the sides and apex spined: tarsi elongated, tapering, ciliated internally, 
5- jointed , terminal joint slender : claws 2 (f), very indistinct in some. 
Decoratus Gyll., Ins. Suec. 2, Add. p. xvi. — Curt. Guide, Gen. 90. 3. 
Ovate, shining, piceous ; antennae ferruginous at the base ; head 
of the same colour, and sparingly punctured, thorax inclining 
to piceous, especially towards the base, wdiere there is a broad 
line of punctures, as well as along the anterior margin : elytra 
strongly punctured with a sublunulate ferruginous -ochre patch 
on each shoulder and another beyond the middle, with the ex- 
ternal margin of the same colour and uniting them : legs ferru- 
ginous. 
In the Author's and other Cabinets. 
