Intermittent streams are dynamic ecosystems that can experience frequent flooding and prolonged dry periods. These changes can be challenging for aquatic invertebrates to inhabit if they are not adapted to these stresses. Waterpenny beetle larvae (Psephenus herricki) are commonly found in Central Kentucky permanent streams, but are also in intermittent streams in karst areas that experience periods of summer-autumn drying. These streams can remain dry for days to months depending on the frequency of rain events and geology. Across the stream beds there can be a variety of benthic substrates from exposed bedrock to areas with rocks and sand. How vulnerable P. herricki larvae are to stream drying and the role particular substrates play in their persistence is poorly understood. Through a series of laboratory experiments P. herricki survival was measured using replicated circular-flow artificial streams to manipulate drying and available substrate types. In the first experiment we exposed larvae to different drying periods: 4, 8, 16, and 32 days without water and a combination of substrates (porous tile to replicate bedrock, cobble, and sand). There was negligible mortality after 4 days dry, but thereafter survival decreased to 30% at 32 days. In a separate experiment, we manipulated the combination of substates (tile, tile+sand, tile+cobble, tile+cobble+sand) and measured larval survival after 8 days dry. Across the treatments cobble presence was key for survival (>40%) than without (<10%), suggesting these rocks may create important humid micro-refuges that are essential to avoid dessication. During the dry periods in both experiments the larvae remained active, likely so they could seek moist refuges and quickly respond when water returned. Our study highlights how an aquatic invertebrate can behaviorally avoid desiccation, but also how the presence of particular benthic substrates may play an important role in whether they are able to persist in intermittent streams.