Massive damage.

Unlike most other enemies that simply stream directly at you, they tend to dodge around a bit which can make them trickery to kill quickly.

They can take out a 15+ armor mech in less then 2 seconds if they pin him down. It is pretty wild trying to fight them. It is day thirty something and attacking a square with them is just about sucide.

15 armor is very light by day 30.
It has been my experience that they are usually the most expensive to fight against as their bullets strip armor. That said, I wouldn't call fighting them suicide.

The bigger tankier bugs, especially ranged ones, can be daunting at first. Remember you can always preview enemy types before a mission. If you’re not ready to deal with them, don’t go in. You can find another way around or even wait them out if you really need to.

As for dealing with them, the main thing is to make sure you’re well equipped. Wear more armor, have more ranged dps, use the priority target menu to have your ranged mech target them. 20+ armor is very doable by the time you’re encountering them regularly, and they don’t do much armor damage if you keep your mechs moving. One railgun or a few cannons can take them down pretty quickly and they don’t have much range. If you don’t have much of those, large missiles w/ fire or mini missiles set to shard can help shred their armor for your miniguns and energy weapons. All else fails, having one or two slow miniguns can immobilize basically any enemy while you kite them. That said they’ll generally keep spawning until there’s three or four on the map, so high DPS is your best bet.

If you need some direction as far as equipment goes, the “Optimus” guide here on Steam is a very good crash course and has a lot of helpful information even for the more experienced player.

The 'gun spiders' seem very weak if fought underwater. Perhaps on the surface they're more of a problem.

Originally posted by ulzgoroth:

The 'gun spiders' seem very weak if fought underwater. Perhaps on the surface they're more of a problem.

This too. While ballistic enemies will still scare your pilots underwater, they’ll do basically no damage. The bug’s missiles on the other hand, are even more deadly down there.