116 PEARSE. 



It might be assumed that U. forcipata was the most abundant 

 species in the locality chosen for these observations, but this 

 was not the case. In order of decreasing abundance the species 

 of this station were: U. rathbunse (about 400 individuals), U. 

 forcipata (275), U. marionis nitida (40), U. marionis (8), U. 

 annulipes (3), U. gimardi (2). 



In addition to their diurnal habits and discrimination in the 

 selection of sites for their burrows, the fiddlers exhibited a third 

 striking peculiarity in their reactions to tidal changes. Countless 

 individuals were to be seen on the flats at low tide, and active 

 feeding was carried on at such a time. The same was true 

 when the sea was rising or falling. When the water threatened 

 to cover the mouths of the burrows, however, a plug of mud 

 was carried to the opening of each hole and drawn down after 

 the owner in such a way as to shut him inside. During a period 



Fig. 1. — Vca rathbun<e carrying a load from her burrow. Drawn from a photograph. 



of high tides, burrows in low situations often remained closed 

 for several days ; during low tides, those on higher ground might 

 be left open day after day, though the flats dried out to such an 

 extent that the crabs could not feed easily, and mostly remained 

 at the bottoms of their burrows. 



BURROWING HABITS. 



In excavating her burrow, a female fiddler digs with the walk- 

 ing legs of either side. After a piece of mud has been pried 

 loose by working under it with the legs it is carried to the mouth 

 of the burrow and deposited outside. The males usually enter 

 their burrows with the small cheliped ahead; and hence they 

 usually carry loads of mud hugged close against the body by 

 means of the first three legs on the side opposite the large chela. 



