Two new spider species from Uruguay, Chaco castanea and Chaco costai, were recently described in the journal Zookeys. Both are middle-sized spiders that range between 1 and 2 cm in body size. Like all spiders from the Nemesiidae family, they have elongated bodies and robust legs with predominantly black-brownish coloration.

The new species are typically found in sandy soils of oceanic and river coastal areas associated with psammophyte, or sand-dwelling, vegetation. This is where the peculiar spiders build their silk-lined burrows where they spend a great deal of their lives. The burrows are also protected by a flap-like door that makes them particularly hard to find.

“Due to a number of life history characteristics, these spiders are difficult to collect and consequently little is known about their biology,” said Laura Montes de Oca, Instituto de Investigaciones Biológicas Clemente Estable, Uruguay. “Observations in natural conditions let us know that they are mostly active during night. This knowledge is key to finding the spiders in order to perform the necessary studies, both in the field and the laboratory. Since they remain in the burrow most of their lives, these animals are vulnerable to habitat perturbations. In Uruguay the psammophyte vegetation is critically decreasing, so it is very important to study and conserve these species.”

The Zookeys article, “Two new species of Chaco Tullgren from the Atlantic coast of Uruguay (Araneae, Mygalomorphae, Nemesiidae),” provides a detailed description of the two news species and a rare glimpse into their living habits.