A Worm's Long Road

Before a hairworm ever steers a cricket, it takes a winding trip. The adult worm releases eggs in water, and the tiny larvae are swallowed by aquatic insect larvae such as mayflies or midges. When those insects grow up, fly to land, and die, a cricket eats the corpse — and the dormant worm wakes up inside its new host.

Now safely hidden, the worm feeds on the cricket's stored fat while sparing the organs it needs to stay alive. Only once the worm has grown does it flip the switch and march its host back toward water, completing a loop that began streams away.