10 STRUCTURE OF ANTS. 



attained, therefore, by far the greatest age of any 

 insect on record. I have also some workers which I 

 have had since 1875. 



The body of an ant consists of three parts : the 

 head, thorax, and abdomen. The head bears the 

 principal organs of sense, and contains the brain, as 

 the anterior portion of the nervous system may fairly 

 be called. The thorax, supporting the legs and, when 

 they are present, the wings, contains the principal 

 muscles of locomotion. The abdomen contains the 

 stomach and intestines, the organs of reproduction, 

 the sting, &c. 



Returning to the head : the antennae consist of a 

 short spherical basal piece, a long shaft, known as the 

 scape, and a flagellum of from six to seventeen (gen- 

 erally, however, from ten to thirteen) short segments, 

 the apical ones sometimes forming a sort of club. 

 The number of segments is generally different in the 

 males and females. 



The eyes are of two kinds. Large compound eyes, 

 one on each side of the head ; and ocelli, or so-called 

 simple eyes. The compound eyes consist of many facets. 

 The number differs greatly in different species, and in 

 the different sexes, the males generally having the 

 greatest number. Thus, in Formica pratensis there 

 are, according to Forel, in the males about 1,200 in 

 each eye, in the fertile females between 800 and 900, in 

 the workers about 600. Where the workers vary in size 



' Having reference to the facts stated on page 37, this is a result 

 of great physiological interest. 



