The worm is Heterorhabditis bacteriophora, a microscopic creature used by gardeners the world over to control insect pests. Its accomplice-in-insecticide is a shiny bacterium called Photorhabdus luminescens, which only lives in the worm’s guts.
When the worm infiltrates an insect, it vomits out the bacteria. These reproduce madly and produce toxins that kill the insect, converting its fallen cells into nutrients that nourish the worm. The bacteria also make amino acids that the worm needs to reproduce, and antibiotics that kill other bacteria trying to colonise the insect. (In the US Civil war, soldiers were sometimes contaminated with P.luminescens, which gave their wounds a mysterious blue shine and protected them from blood poisoning – they called it the “angel’s glow”.)
