Meet Suillia affinis, a small, orange-brown fly belonging to the spiny-winged fly family (Heleomyzidae). Much like their close relatives, these insects are deeply intertwined with the hidden world of fungi. As larvae, they are subterranean truffle hunters, using highly developed sensory organs to locate hypogeous (underground) fungi beneath the forest floor. The adults, meanwhile, play an invaluable role in forest ecosystems by feeding on fungal exudates and inadvertently spreading vital mycorrhizal spores. What truly sets Suillia affinis apart is its rugged resilience. While most insects vanish when the cold hits, this species remains active deep into autumn and winter, and has even been documented wandering across the snow in alpine regions. They are also notably frequently gathering around damp, shaded cave entrances and rock crevices to seek out comfortable refuges when the weather turns harsh. I crossed paths with this fascinating fungal specialist in northern Sweden during my month-long bicycle trip along the Baltic Sea coast.