PHYLUM ARTHROPODA — CLASS INSECTA 339 



In the honey bees, ants, and termites, social life is carried to its 

 highest state of perfection. In these groups the colony is probably 

 perpetuated for hundreds of years. Some ant and termite queens 

 live from ten to fifteen years, building up large colonies consisting of 

 fifty to eighty thousand individuals. Other queens take up the job 

 of continuing the colony. 



A well-developed caste system, also polymorphism, is found in these 

 social insects. In a swarm of bees there are three kinds of individ- 

 uals, males, females, and workers. The workers are females that are 

 undeveloped sexually. Ants and termites have many different forms 

 of individuals in each species. In a termite colony there are many 

 castes. The principal kinds are perfect males and females, or the 

 royal stock, the fecund pair of the colony; a less fully developed 

 sexual caste, with rudimentary wings; a worker caste, of fairly 

 small, sterile, wingless individuals; a soldier caste, morphologically 

 distinct from other individuals because of their large heads and 

 strong jaws; and finally a caste known as nasuti, which are small 

 individuals with the head produced into a kind of snout. Both 

 males and females are found in the various castes of termites. 

 There is also an interesting symbolic relationship existing between 

 numerous intestinal protozoa and the termites. The wood eaten by 

 the termites is made soluble by the infusoria found in their diges- 

 tive tracts. 



Ants are world-wide in their distribution ; they are also very 

 numerous as individuals and species, since about four thousand 

 species are known today. Wheeler believed that ants are the most 

 highly developed as well as the dominant group of social insects. 

 The Formicidae have a highly developed caste system and usually 

 the workers and at times the males and queens are polymorphic. 



Guests 



There are many species of insects that live in the nests of the 

 social insects; these guests are called myrmecophiles when found 

 with ants, and termitophiles when with the termites. Wheeler re- 

 ports that fully two thousand species of myrmecophiles and one 

 thousand termitophiles have been described. Many of the guests 

 have become so dependent upon living with ants or termites that 

 they are never found outside of the colonies. Aphids and mealy 



