The diets of three species of gripopterygid stonefly adults (Acroperla trivacuata, Zelandoperla decorata and Zelandobius furcillatus) from New Zealand were investigated using field studies and laboratory experiments. Guts of female stoneflies were generally fuller than those of males, suggesting that terrestrial feeding was particularly important for females. Adult A. trivacuata and Z. decorata collected from riparian vegetation had fuller guts than those collected from rocks, indicating that adults may move towards riparian vegetation to feed after emergence. Fungi and pollen formed the core food categories found in the guts of adult stoneflies collected from riparian vegetation. Stable isotope analyses of stoneflies and potential food sources collected from the near-stream riparian zone indicated that adult body carbon was derived primarily from autochthonous sources and/or from lichen growing on exposed stream channel rocks. The absence of mature females in our near-stream field collections may explain the lack of congruence between results of gut content and stable isotope analyses, as there would be a time lag between feeding following emergence and incorporation of any terrestrial carbon into body tissue. Assays for the presence of fructose were typically negative, even though pollen and sooty mould fungi were often ingested, probably because nectar or honeydew was rapidly assimilated after ingestion. Laboratory feeding trials indicated that adult Z. decorata lived significantly longer when fed a dilute sucrose solution than when fed a yeast extract solution or water. Our results demonstrate that terrestrial food sources are consumed by these adult gripopterygid stoneflies and that feeding is important for longevity. The provision of dietary requirements for the completion of adult aquatic insect life cycles may be an important consideration in riparian vegetation management. Dietary and assimilation studies of mature females which may move deep into riparian zones are required to resolve the strength of these linkages.