128 PEARSE. 



considerable amount of time had been spent. It would be easy 

 for anyone observing the crabs in a casual way to believe that 

 the males were trying to attract the females by their bright 

 colors, but the writer saw nothing in the behavior of either sex 

 that could be interpreted in that way. The males often wave 

 their claws frantically, as Alcock says, but they apparently do 

 this to an equal extent whether females are present or absent, 

 and without any apparent reference to mating but often before 

 fighting with another male. 



Fiddlers treat other animals with suspicion. Any large mov- 

 ing object causes them to retreat at once to their burrows, 

 although they soon emerge again if the object is not near at 

 hand. Most crabs retreat into their holes when a man ap- 

 proaches within 15 meters, but if one is careful not to make any 

 quick movements he can sit apparently unnoticed within a couple 

 of yards of an active fiddler for hours at a time. Large adult 

 crabs like Sesarma bidens are avoided, but small crustaceans 

 of any species are at once attacked. . Any strange -animal, how- 

 ever small, is avoided; the writer once saw a small hermit-crab 

 cause every fiddler near to run for its hole by moving quickly 

 along the edge of the rising tide. The fiddler's burrow furnishes 

 a retreat from many enemies, and his speedy reaction toward 

 it in response to all movements in his field of vision would help 

 protect him from the herons, snakes, skinks, frogs, toads, and 

 fishes that commonly hunt along the shores of the estuaries. 



In reacting to its surroundings, a fiddler-crab apparently uses 

 its senses of sight and touch most, although the recognition of 

 chemical substances may be important in securing and selecting 

 food. The ej^es are very quick to note any movement in the 

 landscape; they are always held straight upward except when 

 their stalks are being cleaned or when a crab is entering a 

 burrow. Feeding probably depends mostly upon the tactile and 

 chemical senses, for the usual position of the eyes is such that 

 the small chela; can not be seen as they pass food to the mouth. 

 Such loud noises as whistling, hand clapping, gun shots, and 

 locomotive whistles produced no apparent reaction from the 

 fiddlers, nor did the stridulation of the large decapod, Thalassina 

 anomala (Herbst) , that builds its burrows among them. 



GENERAL CONSIDERATIONS. 



Although fiddler-crabs live together in enormous colonies, they 

 show no cooperation with one another, nor do they manifest any 

 tendency toward such communal existence as that displayed by 



