BEETLES. 23 



Cylister Eoeselii, Fabr., much resembles a Dytlscus in size and 

 colour, but is less flattened. 



The genus Hydaticus, Leach, is one of the prettiest of this 

 family. The species are oval, rather flattened, and about half an 

 inch long. They are generally black, with reddish or yellowish 

 markings, or yellowish with black markings, and are far less numer- 

 ous in Europe than in the warmer parts of the world. The elytra 

 of the females are not furrowed. 



The foreign species of Dytiscklm hardly surpass our own in 

 size or beauty. 



Family II. — Gyrinidce. 



Antennae very short ; front legs very long, and rather slender ; 

 hind legs very short and broad; eyes completely divided by the 

 margin of the head. 



The Gyrinidce, or Whirligig Beetles, are among the easiest 

 recognised of any family of Coleoptera. They may be seen on any 

 fine day in summer spinning in circles on the surface of the water, 

 sometimes remaining motionless for a moment, and then either 

 diving or darting off suddenly, or recommencing their erratic dance 

 as before. The Euroi^ean species of Gyrinus, Geoff'r., are small, oval, 

 bluish-black beetles, about a quarter of an inch long. Like most 

 water-beetles they are very smooth and shining. Some foreign 

 species, belonging to the genera Enliydrus, Cast., and Dineutes, 

 Mac!., are nearly half an inch long, and of a violet-blue colour. 



The eyes of the Gyrinidce are perhaps their most remarkable 

 peculiarity, for they are divided in such a manner that the insect 

 has really four eyes, two situated above and two below, so that it 

 can see what is passing above in the air, and below in the water, 

 at the same time. An arrangement very similar to this is met 

 with in the genus Tetraops, in the Loiir/icornia. 



SECTION II.— Palpicornia. 



Tarsi generally five-jointed ; palpi four, maxillary palpi very 

 long, sometimes longer than the antennae ; antennae short, clavate ; 

 habits partly herbivorous, at least in the perfect state. 



Family I. — Hydrophilidce. 

 Body oval ; first joint of the tarsi short, never longer than the 

 other joints ; habits aquatic. 



