Certain spiders and centipedes—despite being separated by more than 500 million years—have independently evolved the same type of venom from an insulinlike hormone. The find, reported today, could lead to greener insecticides and potentially help fight chronic pain and cancer.

Venoms typically evolve from proteins that once served a different purpose. Spiders have been able to turn an insulinlike protein into a powerful poison, for example, thanks to a duplicated hormone gene. But researchers have only just begun figuring out how these duplicates change to become toxic.

Glenn King was particularly struck by an insulinlike venom protein made by hobo spiders, which can kill some crop-destroying caterpillars. For 20 years, the biochemist at the University of Queensland, St. Lucia, in Australia has been hunting for new insecticides by surveying spider and other arthropod venoms. Recently, he and Chinese collaborators found a hormone-derived toxin in centipedes and wanted to know how similar it was to the hobo spider’s version. They carried out a detailed chemical analysis of the protein structure in both creatures.

In other spiders, this venom version of the protein has five spiraling folds, called helices, in its structure. But the centipede and the hobo spider’s version of this toxin had just four of these helices, King and his colleagues report online today in Structure. In addition, their versions had more links between the protein’s folds. Such differences make the toxin more stable than the versions in other spider species that have not been shown to be toxic. They also made the toxin water-soluble, which may broaden its potential application for other purposes. “It may be that this toxin could be a very effective insecticide,” says Jessica Garb, an evolutionary biologist at the University of Massachusetts, Lowell. “People have proposed they could be green insecticides.”

Already, a company in Michigan, Vestaron Corp., has followed up on King’s earlier venom findings and has the U.S. government’s go-ahead to sell a spider-derived insecticide. And now, King is modifying his centipede/hobo spider protein to come up with new uses—fighting chronic pain and cancer or destroying insect pests, for example.

But what appeals to most researchers is what the close resemblance of the two creature’s toxins says about evolution. “It’s cool that it happens in similar ways for two very different and unrelated arthropod groups,” says Trine Bilde, an evolutionary ecologist at Aarhus University in Denmark. But, “it is common in biology that evolution comes up with similar ‘solutions.’ ”