A NEW STUDY from the University of Galway’s School of Natural Sciences has revealed why some spiders possess venom that is far more potent than others.

The researchers analysed venom from more than 70 different spider species, to see if things like body size, prey type, and hunting method, could explain the wide variation in venom strength.

They can now confirm that diet is one of the most influential factors in 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. Meanwhile, it may be far less effective against other non-insect prey, like small mammals.

Lead author Dr Keith Lyons from University of Galway’s School of Natural Sciences, said this could explain why species that are known to sometimes prey on small mammals, such as the Brazilian wandering spider or Black widow, have venoms that can cause medically significant effects in us humans.

“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,” he said.

Dr Keith Lyons and Dr Kevin Healy, School of Natural Sciences, University of Galway Andrew Downes Andrew Downes

The findings were published today in the journal Biology Letters.

The researchers also tested whether the use of webs to capture prey was related to the potency or volume of a spider’s venom.

Dr Kevin Healy, Senior author and Head of the Macroecology lab at the University’s School of Natural Sciences, said that they “surprisingly” found no relationship between the two.

He said this suggests that webs are likely important for restraining prey in web-hunters, regardless of how deadly their venom is.