770 



CLASS IV. INSECTA. 



Fam. 23. Formieidae. The second, and sometimes also the third, ab- 

 dominal segment is constricted fore and aft, so as to form an often irregular 

 " bead " or node ; the fourth segment usually very large ; the trochanters 

 are not divided ; the proximal segment in the antennae elongate, 

 the two forming a scape which bears at an angle a flagellum of eight to 

 eleven segments. This large and diverse family of social insects 

 comprises the Ants. Their mouth is so arranged that the labrum and 

 labium come together and close it between the mandibles, which 

 with the palps lie as it were outside, and to the side of, the mouth. The 

 mandibles can be shut down and firmly locked together over the already 

 closed mouth. The size of the head varies greatly, and even in the same 

 species the workers may have small heads or large heads ; in the latter case 

 they are called soldiers. The stridulating organs by means of which 

 ants seem to communicate with one another, are usually connected with 

 the complex articulation of the base of the abdomen. Ants are active 

 walkers and their legs are long. As a rule, the males are smaller than the 



females. They live 

 in communities, 

 which comprise, be- 

 sides the winged 

 males and females, 

 a number of wing- 

 less workers or 

 neuters. These are 

 in reality aborted 

 females, and, like 

 the functional in- 

 dividuals of that 

 sex, are provided 

 with poison glands. 

 The poison consists 

 of formic acid, 

 which is either in- 

 jected by the sting 

 into wounds, or is 

 ejected, in which 

 case it may get 



into wounds made by the mandibles. Some of the workers, as is 

 the case in the Termites, are specialized as " soldiers " with very 

 formidable jaws and large heads. These defend the ant-hills when they 

 are attacked. The workers survive the whole year, hibernating in cold 

 climates during the winter months. Some of the reproducing females 

 also hibernate, but the great number of both males and females live 

 for a short time only, during the summer. No food is stored up in the ant - 

 nest or " formicarium " for winter consumption, and those individuals which 

 persist through the cold weather become torpid and cease to feed. With 

 the return of spring the females which have survived lay eggs, and these, 

 or in some species the eggs and larvae of the preceding autumn which 

 have lasted through the winter, develop into a new brood, producing 

 males, females and workers. The sexes pair whilst flying through the 

 air ; the males then die, the females cast their wings and either start off 

 to form a new colony or are led back by the workers to the old. After 

 casting their wings the muscles of flight by far the largest in the body 



FIG. 501. Formica 

 male ; c worker ; 

 so-called ant egg. 



(Camponotus) herculanea. a female ; 

 d larva of Formica rufa ; e pupa with case, 

 /, g pupa liberated from the case. 



