Most aquatic benthic insects are amphibiotic,spending their larval stages in water but adult stages on land.A significant proportion of their secondary production is exported to the terrestrial environment following adult emergence,and they are prey of riparian insectivores,hence affecting the distribution of birds,spiders,etc.However,the production of fully aquatic animals,such as Sulcospira hainanensis,the most abundant gastropod in Hong Kong hillstreams,stays in the aquatic environment.This study will determine whether the proportion of annual benthic production remaining in streams attributable to S.hainanensis is greater or less than the production by emerging insects.The results will have implications for the extent of land-water transfers of energy and nutrients along tropical streams,which has received little attention to date.