Entomologists have described two new species of the nemesiid spider genus Chaco from Rocha Province, Uruguay.
Chaco costai, male. Image credit: Montes de Oca L, Pérez-Miles F.
The new species, scientifically named Chaco castanea and Chaco costai, are middle sized spiders that range between 1 and 2 cm in body size.
These spiders have elongated body and robust legs with black-brownish coloration.
Chaco castanea and Chaco costai are typically found in sandy soils of oceanic and river coastal areas associated with psammophyte, or sand-dwelling, vegetation. This is where these peculiar spiders build their silk-lined burrow where they spend 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 Dr Laura Montes de Oca from the Instituto de Investigaciones Biológicas Clemente Estable, Uruguay, who is a first author of the paper published in the open-access journal ZooKeys.
“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”
Chaco castanea, female. Image credit: Montes de Oca L, Pérez-Miles F.
Experiments in laboratory environment reveal some of the secrets that the secluded burrow life of these spiders hide.
Chaco costai was observed during hunting, when the spiders lift the entrance of the burrow with their front legs.
“The flap-like door of the spider den provides a perfect cover to ambush and catch the unsuspecting victim. The spiders return to their burrow after catching the prey. Another occasion when the spiders go in the open is during copulation when both the male and the female leave their hiding places. However, they return to the burrows straight after that.”
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Bibliographic information: Montes de Oca L, Pérez-Miles F. 2013. Two new species of Chaco Tullgren from the Atlantic coast of Uruguay (Araneae, Mygalomorphae, Nemesiidae). ZooKeys 337: 73–87; doi: 10.3897/zookeys.337.5779
