2^0 THE SOCIAL LIFE OF ANIMALS 



and many termites cannot live long if deprived of 

 their associated protozoa, as can be done by appropri- 

 ate treatment in the laboratory. 



The young of both cockroaches and termites hatch 

 out without these essential protozoans. The termites 

 obtain theirs by swallowing a drop of liquid which 

 has just emerged from the anal opening of another 

 termite; the cockroaches get their protozoans by eat- 

 ing the pellets passed from the alimentary tract of 

 molting individuals. Once a cockroach obtains a 

 good supply it renews itself. One such cockroach 

 or a pair can emigrate to a new log and live there 

 for a lifetime. Since, however, adult cockroaches do 

 not molt, the young of such an isolated pair, when 

 hatched, could not receive the so-necessary intestinal 

 protozoa, and hence a pair, if isolated, could not 

 found a new colony. Actually the eggs hatch at just 

 about the time of the annual molting season when 

 the young growing roaches cast their outer covering 

 and a part of the lining of their alimentary tract. 

 At this time the newly hatched young can obtain 

 protozoa readily and thereafter they retain them. 

 The habit of living together is necessary in order 

 that the growing, molting young may transmit their 

 protozoa to the newly hatched nymphs. 



The social situation is still more necessary for the 

 termites. With them all the intestinal protozoans are 



