Source: Kingdom of the Spiders
Location: USA southwest
Threat Assessment: 3. A swarm of many small spiders the size of tarantulas. They are generally more poisonous than on average and attack in mass.
Limitations: Cold bothers them. Can be kept out with a little thought. squishable on a one by one basis. Really it is an exercise in stupid characters that they are the threat they are in the film. (Hint: Check your aircraft for spiders BEFORE taking off.)
Personal Note: One of my favorite films, it is shatnerific!