792 Wisconsin Academy of Sciences , Arts , and Letters. 
Once during the past summer a male was seen to grasp an ad¬ 
versary by the wrist and hold him at “arm’s length” above his 
head. 
From June 28 to August 13, 1912, the writer occupied a 
room in the Marine Biological Laboratory at Woods Hole, Mas¬ 
sachusetts, and had opportunity to extend his observations on 
fiddler-crabs. Fortunately this period cam© during the height 
of the breeding season. It is a pleasure to acknowledge the 
courtesy of those in charge of the laboratory, particularly Mr. 
George Gray. 
Fig 1. Uca pugilator. Two males fighting. The right hand one is 
partly in his burrow. Drawn from a photograph taken at West 
Falmouth, Massachusetts. 
Two species of fiddlers are common in suitable localities in 
the Woods Hole region. Both occur along the sheltered shores 
of estuaries and inlets, where they are usually found among the 
marsh grass (Spartina). The roots of this plant serve to sup¬ 
port the soil so that the crabs’ burrows do not cave in so readily 
when covered by water. Uca pugnax is most often found where 
the soil is of mud or clay ; and U. pugilator is more common on 
sandy beaches ; but the burrows of both species are often inter¬ 
mingled and mixed colonies are not infrequent. Aside from 
these differences in habitat and the fact that U. pugnax bred 
earlier in the season than U. pugilator, no difference was no¬ 
ticed in the behavior of the two species. 
The maximum number of burrows was found about two feet 
(vertical) below high tide mark, and some crabs even had 
holes above the tide limit. Where the tide had covered the 
beach with eel grass or other debris many of the burrows had 
