140 INSECTA. 



ORDER VIII. DIPTERA. 



Body with teguments of the consistence of tender bark ; a 

 trunk forming a univalved sheath, open beneath, and contain- 

 ing a sucker, composed of two, four, or six stiff bristles ; six 

 feet, two membranous wings, above them two movable bodies 

 called halter es. Two palpi; antennae formed usually of three 

 joints; eyes large, commonly three simple ones; thorax occu- 

 pied in a great measure by the mesothorax; abdomen with 

 from four to seven distinct segments; tarsi with five joints. 

 Two divisions. Metamorphosis complete. 



DIVISION I. NEMOCERA. 



Body usually slender and elongated ; head small ; legs long 

 and slender ; wings elongated, and often narrow; antennas fili- 

 form or setaceous, and frequently at least as long as the head 

 and thorax together, and with not less than six articulations. 

 One remarkable genus. 



GENUS CULEX, Lin. Musqueto. 



Proboscis long, slender, projecting, and terminated by two 

 small lips ; sucker with five bristles ; antennas filiform, hairy 

 and downy ; no simple eyes ; wings laid one over the other ; 

 palpi shorter than the proboscis. 



These insects, of which only the females suck blood, show 

 themselves but little during the day, except in the woods. 

 The female lays from two hundred to three hundred eggs, 

 one by one, placing one upon the other, and forming of the 

 whole a kind of raft, which floats upon the water. The res- 

 piration of the larvas who live in this element, is effected by 

 means of a spiraculum, placed at the end of a long tube; this 

 tube serving for the introduction of air into the tracheas, the 

 larva is obliged to live in a reverted position, keeping the 

 extremity of its body upon the surface of the water. 



DIVISION II. BRACHOCERA. 



Body generally wide, and not long; head hemispherical, 

 and of the breadth of the thorax; proboscis sometimes long, 

 slender and coriaceous, sometimes short, thick and fleshy; a 



