308 SPOLIA ZEYLANICA. 
entering, but there appears to be no general rule as to 
whether the larger arm shall be moved into the entrance 
first or after the other arm. In the colonies these crabs do 
not appear to be very pugnacious, and I have never seen 
the large cheliped used as a weapon of offence. In fact, the 
animals appear to find it somewhat unwieldy, and do not 
move it rapidly. Occasionally I saw one crab trespass on the 
feeding ground of his neighbour, but I never saw a fight. 
I have seen one male take hold of the cheliped of another, 
but nothing more happened, so far as I could see. 
Alcock,* who gives a description of these crabs, states 
that “the dismembered chelipeds of the vanquished males 
could often be seen lying on the battlefield.’ I have noticed 

Fia. 1.—Gelasimus protecting its burrow. 
two uses for the large cheliped, in each of which it was used 
as a kind of shield. In one case a male when approached 
by another one, presumably for the purpose of attack, 
crouched down in a small cavity in the ground and covered 
himself with his large arm. In the second case the method 
was similar, except that the crab escaped into his burrow, 
leaving the cheliped to block up the entrance (Fig. 1). This 
was evidently quite intentional, because the animal, instead 


* A. Alcock: A Naturalist in Indian Seas, p. 219. 
