When it spots a target, the Spider will jump down and then fire a large volley of rockets, with a slight delay prior to doing so. When it's done firing rockets, it will either stay and fire more rockets, or jump in the air and land somewhere else. If it is in the air, the rockets fired earlier will hit the general area the target is at. Otherwise, the rockets will hit while the Spider is resting between rocket volleys The rockets do a good damage per rocket.
The Spider's rockets are very powerful, but can be avoided with some timing. First, the player should stay in one area. After the Spider has fired its rockets, run towards it. This will make it will bend down, then jump. As soon as it is in the air, the player should run away from where they currently are. The rockets will completely miss the player. Even if the spider doesn't jump if the player runs to it, walking on and past it will make the rockets miss.
Powerful weapons, such as the LM32 Rocket Launcher and XL4 Lasergun, work best against the Spider. It's high health and the fact that it stays still most of the time makes it very vulnerable to powerful weapons. Spamming these weapons by constantly hitting the fire key will inflict a significant amount of damage on the Spider while its still on the ground.
Gunstacks that have the rocket launcher and MadDog Grenade Launcher work great against multiple Spiders. Spamming them by constantly hitting the fire key will quickly decimate each Spider, especially if the player has unlocked the golden version of either the Rocket or Grenade Launcher or has
The Spider should be a high-priority target when paired with other enemies. It's rockets can seriously damage, if not outright, kill the player if enough connect, and avoiding it's rockets forces the player into locations they may otherwise not want to go to. Killing it ASAP means they don't have to juggle avoiding the Spider's very dangerous rockets while trying to deal with other threats.