by the handling and placement in an artificial environment. In fact, on several 

 occasions when the male member of a mated pair was removed for measuring and 

 then replaced in the container with the female, he immediately grasped her and 

 brought her to the copulatory position. Disturbance actually seemed to inten- 

 sify the males' mating behavior. 



Among the female members of the three mated pairs collected, one was without 

 eggs and two had hatching eggs at the time of copulation. Those with hatching 

 eggs completed hatching soon after copulation. Within 19 hours after copulation 

 (in one case within 6 hours) each of these females had ovulated and deposited 

 new eggs on her pleopods. All new eggs were lost within 2 days after deposition 

 --probably a result of unsatisfactory conditions in the artificial environment 

 in which the crabs were being held. None of the females moulted during the 

 period of observation indicating that the reproductive cycle is independent of 

 the moult cycle or, more likely, that females cease to moult after attaining 

 maturity as happens in other species in the family Majidae (Hartnoll, 1969). 



The larvae that hatched from females held in the wet room were approximately 

 2 mm in total length and exhibited strongly positive phototropic behavior. 

 Because of this attraction to light, the newly-hatched larvae in the natural 

 environment probably occupy the upper portion of the water column at least dur- 

 ing the daylight hours. 



DIEL MIGRATIONS 



Arrow crabs in the coral reef habitat demonstrated a very definite pattern of 

 diel migrations. Observations were made of the specific locations of crabs 

 within the reef habitat during 13 periods at various times throughout several 

 diel cycles. The results of these observations are summarized in Table 2. 



Table 2. --Distribution of arrow crabs on stony and soft corals 

 at various times of the day. 



Total 



Percent of crabs 



Additional observations 



Daylight (0700) 27 



100 



2/ 



All in protected locations 

 All in protected locations 

 All in protected locations 

 All in protected locations 



Most of those on stony coral in 

 exposed locations at or near 

 bases of soft coral 



Crabs descending from soft corals 



About half in protected locations, 

 others in exposed locations on 

 stony coral & moving toward crevices 



All in protected locations 



l_l Combined results of two 

 2^/ Crevices, holes, or und 



observation periods at same time on different days, 

 er overhangs in the stony corals. 



VI-217 



