Northern caddisflies (family Limnephilidae) are large aquatic insects belonging to the caddisfly order, which is closely related to moths. Like caterpillars, their larvae build intricate, wearable armor using silk and local materials such as sand, twigs, and leaves. By undulating their abdomens inside these tube-like cases, the larvae create a continuous current of fresh, oxygenated water across their gills, allowing them to survive even in stagnant ponds. Because they are highly sensitive to pollution and low oxygen levels, their presence is a reliable indicator of excellent water quality and a thriving ecosystem. As adults, they resemble drab moths; however, unlike some of their shorter-lived cousins, they use specialized mouthparts to drink nectar and water to sustain themselves. I met this caddisfly in a forest in Järfälla, Sweden.