INSECTS. 



93 



The body is deeply cut into segments, a peculiarity which 

 explains the origin of the word insect.* In the lower tribes 

 the segments of the body are numerous, and in some cases so 

 many as sixty or eighty pairs of legs may be counted on one 

 individual. From this circumstance the term * ' Myriapoda ' ' 

 has been applied to the Centipede (Scolopendra, Fig. 65), and 

 others of similar organization (Fig. 37). 



In the true insects, the body consists of three portions 

 (Fig. 66); the head, with the " horns" or antennas, and the 

 organs of sensation; the thorax or chest, with the organs of 



Antcnnces 



Eyes 



HEAD. 



1st pair of Legs , : 



l\t pair of Wings 



"2d pair of Legs 



2d pair of Wings 4 



3d pair of Legs 



Tibia 



Tarsus 



..... .-.ABDOMEN. 



Fig. G6. EXTERNAL ANATOMY OP AN INSECT. 



locomotion, whether wings or legs; and the abdomen, includ- 

 ing the organs needful for nutrition and reproduction. 



The heart is an elongated muscular tube, situated along 

 the middle of the back, and hence called the dorsal vessel. 

 The circulating fluid is cold, transparent, and nearly colour- 

 less, f " The action of the heart is accelerated, as in other 



* Latin insectus, cut or notched. 



t "Westwood, Int. to Classification of Insects, page 15, vol. L 



