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 1 875. 



The body of an ant consists of three parts : the 

 head, thorax, and abdomen. The head bears the prin- 

 cipal 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 (gene- 

 rally, 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. 



