The Spider Mine is a type of weapon used by the Helghan Empire.
These are automated area denial devices that cannot differentiate between friend or foe once its movement sensors have been activated. They were development from standard landmine technology and are equipped with a tripodal locomotive system. This allows them to actively pursue enemy forces from beyond their deployed position.
Once within 1 meter of the target, the Spider Mine sets off its anti-personnel charge which, normally, kills the infantry it was pursuing.
The Spider mine concept was most likely based on the Starcraft unit: Vulture. The Vulture is a hit and run hoverbike that is known for deploying Spider Mines, which chases it's targets when within range.
The Spider mine concept was copied in Fallout 3: Operation Anchorage. Walking robotic mines are used by the Chinese forces in Alaska, they also share the same name.