A town in Australia has been infested with a mega cluster of poisonous tarantulas – 25,000 of them.

Maningrida, which is around 500km east of Darwin, has seen the spider population explode and no one knows why.

Arachnologist Robert Raven told the Sydney Morning Herald that clusters normally contain around 200 or 300 spiders in one area but such high concentrations as seen in Maningrida were "off the scale" and "unbelievable".

"Presumably, something is missing that would hammer them or there is something good [such as a food source]," he said. "It's one of the beauties of science, being able to say 'I don't know'."

While the tarantula venom can kill a small animal, it is not deadly to humans. It does, however, cause nausea and vomiting. "These are not shallow bites. Long fangs can potentially do damage by ripping tissue," Raven said.

The species was first discovered in 2006 and is yet to be given a scientific name. It is a species of diving tarantula, which creates air bubbles to survive when its habitat is plunged beneath water during the wet season. This means the spiders cannot be drowned.

Speaking to ABC News, Raven said the species provides a huge opportunity to study the spider venom and create new drugs – which could end up with a big pay day for Maningrida.

"The entire intellectual property concerning the spider – its young, its adults, and its venom – are all property of the community," he said.

"This is a resource for the community in a number of ways... and this could flow back into the community eventually to help them manage the parks better."