372 



EVOLUTION AND ANIMAL LIFE 



is liable to attacks, which it escapes by a rapid retreat into the 

 sea anemone; its enemies in hot pursuit blunder against the 

 outspread tentacles of the anemone and are at once narcotized 

 by the 'thread cells' shot out in innumerable showers from 



the tentacles, and afterwards 

 drawn into the stomach of the 

 anemone and digested.'' 



Small fish of the genus N omens 

 may often be found accompanj^- 

 ing the beautiful Portuguese 

 man-of-war {Physalia) as it sails 

 slowly about on the ocean's sur- 

 face (Fig. 228) . These little fish 

 lurk underneath the float and 

 among the various hanging 

 threadlike parts of the Physalia, 

 w^hich are provided with sting- 

 ing cells. The fish are protected 

 from their enemies by their prox- 

 imity to these stinging threads. 

 Similarly, several kinds of me- 

 dusas are known to harbor or to 

 be accompanied by the young 

 or small adult fishes {Caranx, 

 P series) . 



In the nests of the various 

 species of ants and termites 

 many different kinds of other 

 insects have been found. Some 

 of these are harmful to their 

 hosts, in that thev feed on the 

 food stores gathered by the in- 

 dustrious and provident ant, but 

 others appear to feed only on 

 refuse or useless substances in 

 the nest. Some appear to be of help to their hosts by clean- 

 ing the nests and by secreting certain fluids much liked by 

 the ants. Over one thousand species of these myrmecophilous 

 (ant-loving) and termitophilous (termite-loving) insects have 

 been recorded by collectors as living habitually in the nests of 

 ants and termites. Many of them (they are mostly small 



Fig. 228. — The Portuguese man-of- 

 war, Physalia, with men-of-war 

 fishes, Nomeus gronovii, living in 

 the shelter of the stinging feel^s. 

 (Specimens from off Tampa, Fla.) 



