418 



ANNUAL REPORT SMITHSONIAN INSTITUTION, 1913. 



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Fig. 4.— a fiddler crab closing its burrow by 



pulling down a disk of mud. 



Drawn by Tom Jones. 



Usually the excuvated dirt is carried to a particular spot several 



inches from the mouth of the burrow and placed in a neat pile. The 



speed of excavation varies considerably, but the average time between 



loads is usually from half 

 a minute to three minutes 

 when a crab is working 

 steadily. 



As has been stated, 

 nearly every burrow is 

 closed by means of a tem- 

 porary earthern doorway 

 when the tide comes in. 

 Often the mouth of a hole 

 is prepared by bringing in 

 a bit or two of dirt from 



outside or by carrying up some mud from below. Such masses are 



plastered around the mouth of the burrow and smoothed over to 



make the opening more nearly circular. When all is ready the crab 



goes a little way off and secures a disk of stiff mud (fig. 3) which he 



carries back to his hole. 



This plug he draws down 



in such a way that the 



mouth of the burrow is 



neatly and completely 



closed (fig. 4). When the 



mud on the beach is too soft 



to make a suitable plug, 



mud is pushed up from 



inside the burrow so as to 



close it or the legs are pro- 

 truded a little and the 



opening nearly closed by 



pulling at the soft mud 



(fig. 5) until the small re- 

 maining aperture can be 



easily plugged by jnishing 



up material from below. 



When a fiddler wishes to 



open a burrow that has 



been sealed, he usually pulls 



the door down into the hole, 



where it is left. 



Fiddlers seem to feel that the necessity for having their burrows 



closed when the tide comes in is very urgent. Once in Massachusetts 



I pulled up all the grass on a thickly populated area about G feet 



Fig. 5.— Showing now a burrow is closed from inside. 

 Drawn by Tom Jones. 



