I see you are using Aquaurgist. If you shoot straight up with Water Sine it bounces in place. You can retreat behind that and spiders chasing you through it will get damaged or killed. Continue to move and bounce the Sine straight up, retreat and attack with Sea Slider as necessary. A running shot with your ammo ability could take out quite a few as well. This should work unless you are already at really low health. That many spiders means you will take some hits. But if you can survive for a few seconds and get some kills the health they drop will boost you right back up.
Don't neglect to kill the spawning device on the ceiling either.
Doesnt work when there's that many of them. There isnt a single spell in the game that can take the things out faster than they spawn (sine spells in particular are very slow to fire). The spiders seem to utterly break down if there's more than one spawner in a room at a time, and even with just one spawner, they're still usually a total mess. Finding them to be a very broken enemy in general currently. There's no way to damage the spawners without crashing directly into them most of the time, and the spiders' attacks are utterly unavoidable. No strategy with these guys.... leap in and either keep running, or mash buttons till something happens. Take any health perks you have before going up against them, is the only advice I can give.
They're even worse if they appear during a boss fight right now. The only tactic I have for that is..... switch to Featherweight. Which I hate having to do. Same if you have too many other powerful enemies in the room.