New Spiders Found in Uruguay Hunt From Underground

Two new species of subterranean spiders found in Uruguay have been shown to use their underground nests as a way to trick and trap prey.

Only one or two centimeters long, the spiders Chaco castanea and Chaco costai build silk-lined underground burrows that are covered by a flap-door that makes the nests hard to see and also tactically advantageous for the spiders.

When a prey species passes by, the spiders prop the flap-door open with their front legs and ambush the unsuspecting victim and drag its kill back into the burrow. Outside of hunting, the only other occasions where the spiders were seen leaving the burrows was during mating, however both male and female species of the spiders return straight to their burrows afterward.

The two new spider species were found in the sandy soils of oceanic and river coastal areas with abundant psammophyte, or sand-dwelling, vegetation.

Laura Montes de Oca, of Uruguay's Instituto de Investigaciones Biológicas Clemente Estable, said the spiders, which spend much of their lives within their silky underground burrows, are difficult to collect and study.

"Little is known about their biology," she said. "Observations in natural conditions let us to know that they are mostly active during night. This knowledge is key to finding the spiders in order to perform the necessary studies, both on field and in laboratory. Remaining in the burrow most of their lives, makes these animals vulnerable to habitat perturbations. In Uruguay the psammophyte vegetation is critically decreasing, so it is very important to study and conserve the species"

A scientific paper on the new spider species is published in the journal ZooKeys.