I surveyed treeholes in central Pennsylvania for 7 mo in 1995 to investigate relationships among insect communities and water and leaf litter resources. I used water volume, essential to growth of treehole larvae, as an indicator of habitat size. Leaf litter is the basal food resource in treehole communities, and litter volume is related to the amount of energy available. Insect species richness and larval mosquito (Ochlerotatus triseriatus) and ceratopogonid midge (Culicoides guttipennis) densities were higher in treeholes that maintained high water volumes than those with low volumes throughout the study. Treeholes with high litter volume, irrespective of water volume, had the highest densities of C. guttipennis, and higher total larval densities than those with lower litter volumes; however, litter volume did not affect insect species richness. Scirtid beetle larvae were common in all treeholes, although their densities were unaffected by both litter and water volume. Insect species richness was not related to litter volume, unlike some other studies of phytotelmata. However, my study supported earlier conclusions that both habitat size and resource availability influence structure of treehole communities and maintain species populations. The influence of each resource on particular species presence and density may be related to physical aspects of treeholes, biotic interactions, and natural history of individual species.