Chap. 6 



MUTUAL RELATIONSHIPS OF ANIMALS 



93 



Fig. 6.2. Cooperation. Tent caterpillars and their community web. The young 

 caterpillars spin a dragline of silk from the time they hatch. After a few days of 

 feeding and trial spinning they begin to work together constructing the nest, at 

 first a small night tent, then a larger one a foot and a half or more long. They 

 leave the tent in the day time and creep in single file to a feeding place leaving 

 a trail of silk behind them. (Photograph by Lynwood Chace. Courtesy, National 

 Audubon Society.) 



soundness of the principle have been demonstrated in recent years by the 

 observation, experiments, and conclusions of the eminent American ecologist, 

 W. C. Allee and his co-workers (Suggested Reading, Chap. 6). 



Varieties of Partnerships 



Partnerships may occur between plants, between animals, or between plants 

 and animals. 



Symbiosis. Living together is known as symbiosis. This is a general term 

 that includes all aspects of physiological and ecological association (Fig. 6.4). 

 It is often difficult to determine the exact nature of the relation between two 

 organisms that live together, whether it is a neutral aflfair or an advantage to 

 both partners. In either case, symbiosis would describe it. Commensalism, 

 mutualism, and parasitism are types of symbiosis. 



