INSECTA. 



717 



never less than eighteen, feet, frequently twenty pairs, but never a 

 thousand, much less "ten thousand" feet, as the class name indicates. They 

 are provided with strong forceps or "foot-jaws," which supply a poison for 

 killing their enemies. The millipedes and centipedes are known scientifically 

 as lulidae and Scolopendridae respectively, and in most points of internal 

 arrangement resemble insects, such as breathing by spiracles or (stomates), 

 and trachae or tubes. Some of the centipedes possess electric qualities, and 

 can administer a shock to an opponent. 



INSECTA. 



Insects inhabit the world around us in myriad forms in air and earth 

 and water. Some exist for a very brief space in the air ; others live under 



Antennas - - - 

 Eyes - - - - 



1st pair of legs - 



1st pair of wings- 

 aid pair of legs - 



2nd pair of wings- 

 3d pair of legs 



Head. 



Prothornr. 

 Mesothorar, 



Thorax. 

 Metathorax. 



Abdomen. 



Tibia - - - 



Tarsus - - 



Fig. 843. Anatomy of the external skeleton of an insect. 



-water, or in trees, or in the ground ; some burrow and hide in chinks of 

 rocks and under stones. The numbers are countless, and all have some 

 function to perform as palpably as the busy honey-bee, or as mysteriously as 

 the giddy, careless butterfly. 



Insects are divided into three distinct parts, viz., the Itead, the thorax, 

 and the abdomen, and each of these parts has a pair of legs attached to it, as 

 will be perceived from the accompanying diagram. Along the body are 

 tubes called trachae, for insects do not breathe by lungs, by which the air is 

 carried into the system of the insect, by the "spiracles" or openings of fine 

 network, to prevent dust entering the air-passages. The head is joined to 

 the body by a constricted neck, the part of the body to which it is joined is 

 called the thorax, and to this is added the posterior part or abdomen ; this 



