COLEOPTERA. 503 



The aquatic, carnivorous, pcntamerous Coleoptcra, form a third tribe, that of 



The Hydb0CA.N1 iiari, or Swimmers. 



Their feet are formed for swimming, the four posterior being compressed and ciliated, or in the form 

 of plates, and the two hind ones are far apart from the others. Tin' mandibles are marly covered 

 the upper lip], the body is always oval, with the eyes slightly prominent, and the thorax much broader 

 than long : the hook which terminates the maxilla; is curved from the base ; the ungues are often unequal. 



These insects compose the genera Dytiseus and Gyrinus of Geoffroy. They pass the first and the 

 last state of their existence in fresh water, such as lakes, pools, and ditches. They swim well, and 

 rise to the surface of the water from time to time to respire, ascending easily by holding their feet 

 still and Buffering themselves to float. The body being turned upside down, they slightly elevate the 

 tip of the body above the surface of the water, raising the extremity of the elytra or bending down tin 

 abdomen, so that the air introduces itself into the spiracles, which they cover, and from thence into 

 the tracheae. They are very voracious, and feed upon small animals which, like themselves, ordinarily 

 reside in the water, which the Hydrocanthari only leave at the approach of or during the night. When 

 taken out of the water they emit a very disagreeable odour. They are sometimes attracted by the 

 light into the interior of houses. Their larvae have the body long and narrow, composed of twelve 

 segments, of which the first is largest, with the head strong, and armed with two powerful mandibles, 

 which arc curved into an arch and pierced near the tips ; they have also short antenna*, palpi, and six 

 simple eyelets close together on each side of tlie head. They have six feet of moderate length, often 

 fringed with hairs, and terminated by two small hooks. They are active, carnivorous, and respire 

 either by the anus, or by a kind of swimmerets resembling gills. They quit the water iu order to 

 undergo their metamorphosis into pupae. 



This tribe is composed of two principal genera. 



Dytiscus, Geoff.,* — 

 Which have thread-like antennae longer than the head, two eyes, the fore legs shorter than the fol- 

 lowing, and the posterior often terminated by a compressed tarsus finishing in a point. Thej swim 

 with great quickness by the assistance of their feet, fringed with long hairs, especially the posterior 



pair. They dart forward upon other insects, aquatic worms, &c. In the majority of the males the 

 four anterior tarsi have the three basal joints dilated and spongy beneath ; those of the first pair arc espe- 

 cially remarkable in the large species, in which these three joints forma broad plate, the under surface of 

 which i- covered with small bodies, some of them like warts and others like small suckers. Some females 

 are distinguished by then elytra being furrowed. The larva: have the body composed of eleven or twelve 

 segments covered bj scaly plates ; they are long, swollen in the middle, and slenderer at each end, especially 

 when the terminal segments form an elongated cone fringed at the sides with Boating hairs, with which 

 the animal beats the water and thus propels the body forwards, which is ordinarily terminated by two 

 conical bearded and moveable filaments, between which arc two small cylindrical bodies pierced with 

 a -utter, at the extremity which arcaenal channels, to which arc attached two traehi 82 ; moreover, the 

 sides of the body are provided with spiracles : tin' head is large, oval, attached to the thorax by a neck 



with strongly-armed mandibles, beneath the extremity of which De Geer observed .1 longitudinal slit, so 



that these organs resemble the mandibles of the larva' of the M\ rmeleons, or Ant-lions, and serve them 

 for suckers: the month offers besides a pair of maxilla- anil a lip with palpi : each of the three first 

 segments supports a pair of moderately Ion- legs, of which the tibia and tar-us arc fringed with hairs, 



which are serviceable in swimming ; the firsl segment is the broadest or and defended beneath, 



as well a> above, bj a scaly plate. 



These larVSe suspend themselves at the surface of the water DJ means of two appendages .it the sides 

 of the tail, which they keep drv by raising them abOVC the surface. When they wish to change their 



place suddenly, the; give their body a quick and vermicular movement, beating the water with the 

 tail. They especially feed upon the larva- of Dragon-flies, Gnats, Tipulse, Ajelli, &c. When the period 



Of their transformation has arrived, tiny quit tin' water and bury themselves under the earth of the ad- 

 jacent banks, keeping, howe\er, in very damp situations. Where thej form an oval eavitv in which they 



• [I fcoj M (lie Author of Ihr CnOtjmry, COrrCCttd ll lu IMuu,, l.cin* .' • t.rrrk 



■'Troy, on ihr tiu. 1 



