Pearse—On the Habits of TJca Pugnax. 
791 
ON THE HABITS OF UCA PUGNAX (SMITH) AND 
U. PUGILATOR (BOSC). 
By A. S. Pearse. 
Zoology Department, University of Wisconsin. 
Fiddler-crabs are remarkable chiefly for the great size of 
one of the chelipeds on the males. The enlarged claw may oc¬ 
cur on either the right or left side. The females have two small 
chelipeds similar to the lesser one of the males. The use of the 
monstrous claw has been a matter of much speculation; it has 
been variously supposed to serve as a stopper for the burrow, a 
spade for digging, a weapon for combat, a “nuptial couch” 
used during copulation, and to attract the admiration of the 
females. Smith and Weldon (’09), though they review the 
opinions of other writers, do not commit themselves as to the 
use of this peculiar structure. Alcock (’02) believes that it 
is used as a sort of flag, which is waved to attract the females. 
Caiman (’l'l) in his recent “Life of Crustacea” says (p. 106), 
“What the precise use of this enormous claw may be does not 
seem to be quite certainly known. It is said to be used as a 
weapon by the males in fighting with one another, but it seems 
too clumsy to be very efficient for this purpose. It is often 
brilliantly colored, and has been supposed to be a sexual adorn¬ 
ment.” 
The writer (’12) has shown elsewhere that fiddlers use their 
great claw with marked agility in combats with each other; 
indeed, one crab may throw his adversary three or four feet, 
and, as many such, contests have been observed (fig. 1), there 
seems to be no reason to doubt the claw’s efficiency as a weapon. 
