8o evolution: the ages and tomorrow 



young nymphs which may become sterile workers, or sol- 

 diers of either sex, or reproductive individuals. When the 

 colony is established, the presence of mature males, or fe- 

 males, or soldiers prevents the formation of any more of 

 these castes, and the nymphs produce only sterile workers. 

 It is assumed that the soldiers or reproductive individuals 

 give off some chemical substance which, when in sufficient 

 quantity, will prevent further production of these castes. 

 New colonies are founded by the flight of winged repro- 

 ductive individuals which then lose their wings. Termites 

 are essentially wood eaters, although they are themselves 

 unable to digest wood. This is done by countless protozoa 

 which inhabit their digestive tracts. Individuals of the 

 colony cooperatively infect each other and the young with 

 these protozoa at every molt. Here the benefits of the social 

 organization are very obvious. Termites could not lead sol- 

 itary lives. By socialization they not only gain the capacity 

 to digest wood, but they also eventually evolve means for 

 social protection (soldiers) and control over the environ- 

 ment. Living today are both primitive and very advanced 

 species of these insects which, apparently, were evolved 

 from unspecialized ancestral forms related to the cock- 

 roaches. Termites are of lowly origin as compared to other 

 insects but have, nevertheless, been able to evolve complex 

 and highly efficient social systems. The higher tropical ter- 

 mites have an incredible talent for architecture, their nests 

 being huge structures sculptured with such amazingly exact 

 detail that the species can be determined by examining their 

 housing. 



In the honeybee the queen and the workers are developed 

 from fertilized eggs and are genetically alike; the drones 

 (males) are developed from unfertilized eggs. Queens are 

 produced by a special nutritive treatment, the egg which is 

 to be so treated having been placed in a larger, peanut- 

 shaped cell in the comb. The drone, although receiving the 

 same nutritive treatment as the workers, is developed in a 



