Habits, Reactions, and Associations in Ocypoda arenaria. 9 



will run into their burrows for a few inches and push a plug of sand up from 

 below, completely closing the entrance. 



It seems probable that not more than one ocypoda at a time makes a 

 burrow its home, unless during the breeding season, although I have seen as 

 manv as three emerge from a single hole. Most of the burrows are not 

 permanent living-places, since they are usually made below high tide. In- 

 dividuals often drive one another out of their burrows, and the successful 

 one usually appropriates the new home that it has won ; on several occasions 

 three in succession have been seen to gain possession of the same burrow. 



BREEDING SEASON. 



The breeding season of Ocypoda was practically at an end when I visited 

 Tortugas in June, but my own observations and those of others lead me to 

 believe that it occurs probably in the spring and early summer rather than 

 throughout the summer, as suggested in my preliminary report. During the 

 late summer of 1906 I examined many female specimens, but only in a few 

 cases did I find any eggs, and these were always few in number, suggesting 

 the last of a brood. Mr. Kellner, who was at Tortugas as early as March, 

 states that at that time large ocypodas were quite scarce, but that very little 

 ones were quite numerous. Later, however, according to his observations, 

 the adults began to appear again, so that in June they were present in con- 

 siderable numbers. It seems very probable that farther north along the 

 Atlantic Coast the breeding season is somewhat later. 



There is scarcely any difference in appearance between the male and 

 female ocvpodas, except in the shape of the abdominal segments (plate 3) 

 and the abdominal appendages. The females, however, are usually clean- 

 looking and less scarred than the males. Both have the stridulating ridge, 

 of which I shall have something to say later (page 28). 



During the time that I was at Loggerhead Key the males seemed to be 

 much more in evidence than the females. In nearly every case when 

 burrows were dug up and individuals were found inside they were males. 

 The traps also always showed a larger number of males than females. 



FOOD AND FEEDING. 



Ocypoda is often found feeding during the daytime, but more especially 

 at night (plate 2, fig. b). It is also a cannibal, and to test this characteristic 

 a small trap was stocked with many small individuals measuring from i to 2 

 cm. across the carapace. During the night two larger individuals, about 4 cm. 

 across the carapace, dropped into the trap and in the morning most of the 

 small ones were found torn to pieces, with the soft parts eaten out. It is 

 interesting to note that when a trap is set only large individuals are found 

 as a rule in the morning. In a trap which had caught 30 ocypodas during 

 several nights no small ones were found, and it seems probable that they 



