Experiments have been carried out on the duration of larval development of the spider crabHyas araneus L., in relation to temperature, food quality, and individual variation. A graphical model is presented which predicts larval occurrence and settlement in the field (Helgoland waters, North Sea). Preliminary observations are reported on predator-prey interactions with larvae of the spionid polychaetePolydora ciliata. Cannibalism and necrophagy during starvation experiments with zooplankton are considered: In larvae which are not kept in individual confinement, maximum survival time doubles due to feeding on living or dead sibling larvae. Analyses are presented revealing elemental and biochemical composition of starved and fed larvae as well as energy equivalents calculated from these data. During starvation, early larvae lose carbon, nitrogen, and hydrogen. Their main metabolic substrate is protein; lipid is utilized to a much lesser extent. Exoskeleton formation is, apparently, independent of nutrition: Zoea-1 larvae starved for 8 days contain the same amount of chitin as larvae fed well over this period of time. Energy calculations suggest an extremely low respiration rate and a very effective reconstruction of body material in starved larvae.