236 



The Evolution of Communities 



below the fruiting body have become white and form a typical 

 flowerlike structure (Fig. 101) (Leppik, 1955). 



Fig. 101. The sedge Dichwmata ciJiaia in which the leaves at the base of 

 the flowering structure resemble a flower. ( From Leppick. ) 



The "guests" of ants and termites include beetles, flies, mites, 

 and other predators, but some of them undoubtedly classify as 

 commensals or some type of symbiont (Emerson, 1949). The scav- 

 engers which feed on refuse in the nest (some of the flies and 

 beetles) would classify as commensals. Some of the predators and 

 parasites secrete exudates which the hosts lick from special body 

 areas and, by contributing this much to the diet of the ants, may 

 be considered some kind of a symbiont. It is easy to rationalize 

 the evolution of these exudatory areas by the colony guest as a 

 means of protection in the ant colony. 



The echeneid fishes (Renwra and its allies) which attach to 

 sharks and other fish by means of a sucker-like disc on the eche- 

 neid's head are another excellent example of mutualism. Some 

 echeneids feed on zooplankton and smaller fishes; they may attach 

 themselves to sharks and other fish mcrclv to rest or to be trans- 

 ported to new feeding grounds. A second group of echeneids feed 

 chiefly on scraps from their host's meals and the host's feces. A 



