There appearance was similar to other arachnid-like animals throughout the galaxy. The cave spiders ranged in sizes from smaller than a Human fist to as large as an average Human. They were able to shoot both venom and sticky webbing at enemies. Their caves could be detected by the discarded webbing.
Although supposedly non-sentient, they were very intelligent. They hunted in packs and the packs were able to change tactics in the middle of an attack. This indicated at least rudimentary communication of some kind. They were also able to perceive when invaders were no longer a threat. The cave spiders were fiercely territorial having to defend their caves against the X'Ting, the dominant sentient species on the planet, who also lived in caves tunnels.
A group of clone troopers, lead by Obi-Wan Kenobi and Kit Fisto, encountered a group of these cave spiders on a mission to Ord Cestus. After deaths and injuries on both sides, the Jedi backed off and let the remaining spiders live. One spider made a motion that could be interpreted as a bow of respect as they retreated, although this could have simply been anthropomorphism on the Jedi's part. Later on, a group of spiders attacked a JK-13 organodroid. When the larger spiders had no effect, smaller spiders started to swarm and confuse the droid. Although they were merely defending their territory, their actions (intentional or otherwise) had the effect of saving ARC Trooper Jangotat's life.