Two species of ocean skaters, Halobates germanus and Halobates micans, live in the tropical and subtropicalwaters of the Indian Ocean. From December 1992 to December 1993, Halobates was intensively sampledin the easternmost region of the South Indian Ocean (13–18.5°S, 114–121E°), from which there have been a small number of records of Halobates. No H. germanus was caught, but a total of 1190 H. micans were collected, with densities estimated at 13 900–28 100 individuals/km2. This suggests that H. micans lives in the study area at high densities comparable to those in the Atlantic and the Pacific Oceans. We also discuss the possible effects of ocean currents and winds on the geographic distributions of the two Halobates speciesin the eastern South Indian Ocean.

Specimens of ocean skaters Halobates were collected off the south coast of Japan in the East China Sea in 1995, and from the Kumano-nada Sea to the East China Sea in 1998 and 1999. Three species were identified: H. micans, H. germanus and H. sericeus.  We found two species co-occurring in comparable densities in different years, a phenomenon not hitherto reported in other regions of the ocean. We discuss distributions of the three Halobates species with special reference to the influence of the Kuroshio Current, temporal variations of sea-surface temperature, and monsoonal winds.

Five species of ocean skaters Halobates are the only insects that have successfully  colonized the ocean.  In the western Pacific Ocean, three species of Halobates, H. micans, H. sericeus and H. germanus, are known to occur over a wide area. We investigated the spatio-temporal features of Halobates during the three cruises of R/V Hakuho Maru in the western Pacific in 1994, 1995 and 1998. During these cruises, the area between latitudes 7^o N - 22^o N and longitudes 125^o E - 150^o E was surveyed in all cruises, and in this area H. germanus was absent while H. micans and H. sericeus were caught every year. In 1994 and 1995, H. micans was found almost to the exclusion of H. sericeus and in 1998 H. sericeus was found almost to the exclusion of H. micans, suggesting that these two species rarely co-occur, while their distribution ranges change temporally. We examined water surface temperature, prevailing winds and the El Nino event as possible factors responsible for the replacement of H. micans by H. sericeus in 1998. 0n the ocean surface, oceanic diffusion is constantly acting to disperse  Halobates in all directions. However, local distribution patterns of H. micans and H.  sericeus were highly clumped, suggesting that these species have the ability to aggregate against oceanic diffusion.