Odd Clawed Spider That Builds Ladder-Shaped Webs Discovered in Australia

Posted on September 25, 2013

Progradungula otwayensis

A spider described by scientists as mysterious and "odd-clawed" has been discovered in Victoria, Australia. The spiders reside in the hollows of old myrtle beech trees in Great Otway National Park. Progradungula otwayensis belongs to the small spider family Gradungulidae.

P. otwayensis is a species of spider with a cribellum, a web producing organ which produces extremely fine fibers. The researchers say the fibers of the web are so small in diameter that prey insects easily become entangled in them, without any glue needed. P. otwayensis weaves ladder-shaped webs. The spiders stand facing down after sunset, waiting for preys which will be caught by using the ladder as a trap. A thick and shiny silk is used by the spiders to provide a zip-line like connection between external webs and its retreat in the hollows of ancient myrtle beech and mountain ash trees.

Peter Michalik, Zoological Institute and Museum of the University of Greifswald (Germany) and lead author of the study, said in a statement, "On one occasion, we had access to a large hollow mountain ash tree and found catching ladders and supporting webs of juveniles inside of it."

The image below shows one of the spider's catching ladders in front o f a hollow in a large fern tree. The red arrow is pointing at the web. Take a look:

Catching ladder web of Progradungula otwayensis

The research was published here in ZooKeys.

Photos: Martin J. Ramirez