Shockarachnids resemble largely oversized spiders with eight red eyes, eight claw-tipped jointed legs and a large abdominal section. They have a pair of fangs that are able to protrude from their "mouths" and emit a highly-charged current of red electricity that can be applied to a selected target. Their abdomens also have a built-in steel spool producer hidden in the very tip.
A larger version of the Shockarachnids with retractable wheeled feet, most likely the leader appeared in "Diamond Bit".
Shockarachnids use their electrical bites to cause other mechanical creatures, namely Trux and Tools alike to malfunction; they also produce a type of web possibly made out of flexible steel fibers capable of being used in construction during builds. The metallic silk also exudes a strong magnetic field that can trap other living organisms made out of metal and make getting out of a web next-to-nigh-impossible.
Though they're called Shockarachnids they should've been called Shockarantulas. <- according to this person