What is that terrible smell? Is it spoiled fruit? A rotten egg? A dead animal? It’s actually coming from this cage fungus —  which is in the absolute prime of its life. That horrible smell is part of an  elaborate hoax to fake its own death. Like most mushrooms, what you see is  only a small part of the organism. The vast majority is hidden below  the surface — in an expansive   network of miniscule threads called the mycelium. Cage fungus is saprobic — the  mycelium eats dead and rotting wood,   digesting the cellulose and  returning nutrients to the soil. When the weather is warm and wet  and there’s plenty of wood around,   the mycelium creates an “egg” — this  brain-looking thing — that pops up above ground. A white leathery membrane protects  the egg as it grows and stretches. Until it cracks open. The spongy lattice bursts outward. After a few hours it looks — and smells  — like a basket made of decaying flesh. The interior surfaces of the lattice are  coated in a sickly brown slime called gleba. That horrendous odor emanates  from those sticky globs. The open lattice shape helps  the stench spread in the breeze. But to a fly, that reek is irresistible. It screams: rotting carcass! A delectable  meal, or a place to lay their eggs. The gaps in the lattice are just the right  size for the flies to pop in and out. They traipse around, gobbling up the goo. The flies love it, but  what’s in it for the fungus? Well, the fungus needs something  that the flies have — wings. While many mushrooms spread their  spores by releasing them into the wind,   the cage fungus gets the flies to do all the work As they feed, the flies unintentionally down  millions of the fungus’ microscopic spores,   hidden inside the dark slime. The gleba also clings to the flies’ feet. When the flies lift off, they take the spores  with them, spreading them far and wide. After about a day the lattice starts to collapse. Having successfully spread its spores,  this is the end of its story — or is it? When the conditions are right, the  fungus will pop up more eggs year