1. 1. Lipofuscin, body carbon and respiration rates were measured in Hyas araneus from hatching to metamorphosis. Lipofuscin was measured spectrofluorometrically from the chloroform phase of chloroform/methanol extracts. 2. 2. Excitation/emission spectra of both the chloroform and the methanol/aqueous phase showed one distinct fluorescence peak in the chloroform (410-415 nm emission/340-350 nm excitation) and the methanol/aqueous phase (405/350 nm) of zoea I (directly after hatching) and megalopa (0 and 24 days old). 3. 3. Individual lipofuscin concentrations increased continuously during zoea I and halfway through zoea II, but remained constant through the entire megalopa despite high metabolic activity in this stage. 4. 4. Individual lipofuscin concentrations were positively correlated with body carbon and carbonspecific lipofuscin was negatively correlated. 5. 5. Moulting caused considerable loss of lipofuscin. During the first two larval ecdyses 17-18% were lost, with the shed moults containing only 3.4-4.5% of the lipofuscin found in late premoult individuals. 6. 6. The different patterns of lipofuscin accumulation in respective larval stages is discussed in regard to mitotic activity of tissues. While in the zoea, growth is more related to lipid formation and biomass accumulation, in the megalopa morphogenetic processes require substantial epidermal growth, i.e. protein accumulation. However, the question why in the megalopa no increase in lipofuscin is found, remains unanswered. © 1987.