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For instance, a bite from the Brazilian wandering spider can result in serious medical complications, whereas the venom of a giant house spider typically poses no threat to humans, raising the question, what drives such differences in venom potency?

The researchers discovered that diet is one of the most important drivers influencing the potency of spider venom. They found that spider venoms are what is called prey-specific, meaning if a spider primarily hunts insects, its venom is likely to be particularly effective at killing insects in general, such as crickets and flies, but far less effective against other non-insect prey, like small mammals.

Our results show that spider venoms have evolved to be especially potent when tested on animals found in their diet in the wild.

This may explain why species that are known to occasionally prey upon small mammals, such as the Brazilian wandering spider or Black widow, have venoms that can cause medically significant effects in us humans, whereas species that only prey on invertebrates, such as the Giant house spider, have evolved venoms that target invertebrate physiologies rather than our own, posing little threat to us.