A newly identified species of trapdoor spider, a burrowing spider known for building concealed doors over the entrance to its home, has been discovered living in an unlikely place. It survives daily flooding of its home by creating a waterproof door over its burrow. The Mauritian tidal trapdoor spider, scientifically named Idioctis marevallum, was discovered on tiny islands off Mauritius in 2023 and formally described as a species new to science in April 2026.
Durrell Wildlife Conservation Trust, which was involved in the discovery, announced the finding on October 27. Researchers have described the spider as an "endemic species of intertidal trapdoor spider," which means it’s native to Mauritius and lives in areas regularly flooded by seawater. It belongs to the Barychelidae family, which is a broad group of mygalomorph spiders that includes tarantulas.
Mygalomorph spiders tend to have large, powerful fangs and thick, hairy bodies and legs. But perhaps the most remarkable feature about this spider is how it copes with the ocean. Researchers found that they nest in coastal areas that are either completely submerged by seawater or struck by waves every day.
They survive by digging burrows and building trapdoors (hence the name) that stop seawater from flooding their homes. Scientists from the Durrell Wildlife Conservation Trust initially thought that the spiders might be Tigidia mauriciana, another Mauritian trapdoor spider, which was discovered in the 19th century and has only ever been detected once, but examination of their anatomy eventually ruled that out. So far, researchers have only found the spider on Ilot Vacoas and Ile aux Fouquets, two islands in the Mauritian archipelago, the group of islands that make up Mauritius.
The species appears to have an extremely limited range, with researchers recording its presence across just 227 square meters of habitat on Ilot Vacoas and 686 square meters on Ile aux Fouquets. The spiders live in hard coralline rock in the intertidal zone, which is the part of the coastline that lies between the high-tide and low-tide marks. They like to nest on the southern sides of the islands where the waves are strongest.
The researchers searched other seemingly suitable areas but didn’t find any additional nests. Their homes are tube-shaped and about 12 centimeters, or 4.7 inches, long, lined with webbing and sandy material. The trapdoor is made from rock, sand and algae, which not only stops their residence from flooding, but also helps it blend into its surroundings.
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