Hidden along calm waters across Europe, Sisyra spongeflies lead a life of dramatic biological turns. As delicate adults, these miniature insects—measuring under ten millimeters across—resemble brown lacewings and flutter softly during twilight hours, feeding on sweet honeydew, flower pollen, and tiny mites. Yet, their upbringing is pure sci-fi. Beneath the lake’s surface, Sisyra larvae are ferocious, highly specialized predators that target freshwater sponges. To survive underwater, they possess a feature unique among all living insects: seven pairs of flexible, jointed gills lined along their bellies. Using long, needle-like mouthparts, these aquatic grubs pierce the soft tissue of living sponges to drink their cellular fluids. Once fully grown, the larvae leave the water behind, crawling onto tree trunks or rocks to spin double-layered silk cocoons where they spend the winter. As spring arrives, they emerge as graceful winged fliers to start the cycle anew. I encountered this cute spongefly perching quietly on the bank of a postglacial lake in the Järfälla Nature Reserve, Sweden.