SOCIAL TRANSITIONS 27 1 



lost with each molt, and each time that happens 

 each newly molted individual must obtain some of 

 the protozoans from another member of the colony 

 or it will starve. The newly hatched termites often 

 obtain protozoa before they are twenty-four hours 

 old, and an artificially defaunated termite, if allowed 

 to associate with his normal fellows, is reinfected 

 within a few days. With the termites, colony life is 

 an absolute essential and only the winged males and 

 females, the first form reproductives already infected 

 with protozoans before taking the nuptial flight, can 

 even start a colony without the presence of others to 

 carry the needed cultures of protozoans. 



Many cockroaches which neither eat wood nor 

 harbor wood-digesting protozoans reproduce so 

 rapidly that given good hiding places and plenty of 

 food they aggregate in large numbers, as many 

 housewives know. These cockroach aggregations, 

 which appear to be formed as a result of tropistic 

 reactions to the environment, accompanied by tol- 

 eration for the presence of others, permitted the 

 wood-roach Cryptocercus to develop the habit of 

 passing protozoa from one individual to another, and 

 so began the long evolution which has resulted in the 

 highly adapted, wood-eating roaches found today. 



The same basic adaptation allowed their relatives, 

 the termites, to start on the much longer road they 



