HABITS, REACTIONS, AND ASSOCIATIONS IN OCYPODA ARENARIA. 



By R. p. Cowles. 



One of the most interesting crustaceans that inhabits the Atlantic Coast 

 of the more southern States is the brachyuran Ocypoda arenaria, the so- 

 called " sand-crab," and no one who sees this lively creature can help marvel- 

 ing at the rapidity and dexterity of its movements as it scampers over the 

 beach sands. While the adult has not been reported north of New Jersey, 

 Verrill (1874) tells us young specimens have been seen by Mr. S. I. Smith 

 at Fire Island, Long Island, by himself at Block Island, Rhode Island, and 

 that the niegalops larva has been taken in abundance by Mr. Vinal Edwards 

 in Vineyard Sound. Verrill has suggested that ocypodas found in the 

 Northern States are carried there from the South by the Gulf Stream while 

 in the larval condition and that each winter they are killed off by the cold 

 weather, so that they never grow large enough to breed. This supposition 

 seems to be very plausible, since none but half-grown specimens are found 

 in those regions and since breeding occurs in the South at just about the 

 right time to make it possible for larvje to be carried up in the early spring. 

 The adult has been reported from Cobb Island, ^^irginia, and it is very 

 common along the sea-beach in the region of North Carolina. It flourishes 

 in the Bahamas, on the sandy keys of Florida, and is found as far south as 

 the coast of Brazil. 



During the summers of 1905 and 1906 it was my good fortune to spend 

 a few weeks in the Marine Biological Laboratory of the Carnegie Institution 

 of Washington at Loggerhead Key, Florida. On this key specimens of 

 Ocypoda arenaria were very abundant, and owing to the small size of the 

 island it was an easy matter to study them at all times of the day while only 

 a short distance from the laboratory. A preliminary report of my observa- 

 tions during the summer of 1905 has been published in the Year Book of 

 the Carnegie Institution of Washington, No. 4, 1905. 



My purpose in studying Ocypoda was to learn as much as possible con- 

 cerning its behavior and to determine how far it was able to form associa- 



te V ?^'^Ar' express my thanks to the Carnegie Institution of Washington and to 

 Dr. A G. Mayer, Director of the Marine Laboratory at Tortiiga?, for manv courtesies 

 extended to me. 



