Invisible Arachnid

The Invisible Arachnid is a pervasive, phobia-inducing spider that soldier will come to loathe as he explores the UNN Rickenbacker. While not truly invisible, those Arachnids are significantly harder to see and present a bigger challenge for the soldier. They like to hide in the dark corners of the Rickenbacker where they are first encountered, and leap up at him when he least expects it.

Strategy
In truth, Invisible Arachnids aren't significantly tougher to deal with than the Adult versions, as they have the same number of Hit Points, the same Toxic damage potential, and attack with the same swarming and leaping behavior. It's easy to justify spending ammo on these, especially in the late game when it's plentiful, though it's recommended you save any Worm Clusters you might have for the massive number of Rumblers you'll encounter later on. As always, keep several Anti-Toxin Hypos on hand, or you'll suffer long after your enemies are dead.

Invisible Arachnids are not invisible to the Enhanced Motion Sensitivity Psi Power. They also don't respawn, and they're not very plentiful to begin with. Keep your radar active the first time you're moving through the Rickenbacker and you should be fine.