The koa moth (Scotorythra paludicola) is a species of moth that has been reported to irrupt in great abundance on occasion over the past 100 years, sometimes defoliating its host plant, koa (Acacia koa), during the event. This data release includes metadata and tabular data that document the amount of frass (caterpillar excrement, which is a proxy for foliage consumed) produced by koa moth caterpillars as they mature through their five larval instars (life stages). In the lab, frass was collected from individual caterpillars representing instars 3, 4 and 5, dried and weighed. From these data, a significant relationship was found between caterpillar instar and the amount of frass produced, which allowed indirect estimates of frass production for instars 1 and 2. The weight estimate for each instar was used to estimate total amounts of frass produced by caterpillars at different times during the outbreak that defoliated much of the the koa at Hakalau Forest National Wildlife Refuge during 2013-2014.