MOUND BUILDING IN ILYOPLAX-PINGI (CRUSTACEA, BRACHYURA, OCYPODIDAE)

The ocypodid crab Ilyoplax pingi, observed in Kanghwa I., Korea in 199 2, builds a mound at the burrow entrance, by piling mud dug out from t he burrow. The mounds were made by both waving and non-waving males, a nd by both ovigerous and non-ovigerous females. The burrow diameter at the widest part tended to be larger in crabs with mounds than in crab s without mounds, whereas the burrow depth was not different between t hem. The mound density increased in the late exposure period, when the crabs' surface activities declined. Mound removal and rebuilding expe riments revealed that the presence of the mounds has the effect of kee ping neighboring crabs away.