The final version of this level will have the spiders drop in from a damaged building rather than just appear but the spawning stays.
I think we've all got a little too used to linear games where you see the enemy right off, deal with them and then move forward at top speed. Spawning enemies keep you on your toes.
You'll maybe have noticed that the toxic waste sheds that some of the spiders crawl out of emerge into up to three different parts of the level allowing me to use the same spider enemy three times and with a limited spawn life thus saving on too many entities.
The spiders are fast and incredibly strong but I like that.
The one life with only a hundred health is more than enough for any decent gamer to reach the train with at least quarter health and around 50 bullets left over.
If you find the spider spawn annoying the zombie level under construction will really annoy you as based on the theory that zombies are already dead you can't kill them just avoid them.
Having to complete a mission with zombies stalking you is creepy especially if you go down a dead end alley.