Continuity mistake: When they perform the autopsy on the three victims, Metcalf is all grey and stiff, whereas the two exhumed victims look alive and fresh.
Factual error: With Irv and Blaire, one of them picks up the handful of popcorn and presumably eats the spider. While inside the eater, the spider would bite and poison whoever it was inside. When they find both of them dead, the spider crawls out of one person. Why would it leave one body and actually take the trouble to go inside the other rather than just bite them on the skin like the others? It's not like it would crawl out and back into the bowl to be eaten by the other person.
Suggested correction: We actually don't see either Irv or Blaire "eat" the spider at all. We just see Blaire take a handful of popcorn with the spider inside. Next we see both dead bodies, and then a spider crawls out of Irv's nostril. So the spider could have bitten both people on their skin in short order and then crawled into Irv's body, for whatever reason, after he was already dead. Or, there could be two completely different spiders that killed the pair at around the same time. As the action happens off-screen, it can't be a factual error, we simply don't know exactly what happened.
The whole scene doesn't make sense. The fact that Irv pours the butter on the popcorn with the spider in the bowl, Blaire doesn't feel the spider in her hand when she picks it up with the popcorn, and they are still sitting in the same position watching Wheel of Fortune after being bitten. Only Irv's Coca-Cola can is lying on the floor with some popcorn pieces. The popcorn bowl is still on Blaire's lap, showing they did not have seizures to the spider's venom like the other victims. It also doesn't make sense that the spider doesn't bite Irv when he carries the bowl from the kitchen to the living room.
The mistake entry as written states that the spider is eaten by one person and then eaten by another, with both people dying afterwards. Since we do not actually see that happening, this doesn't count as a Factual Error. The fact that the victims do not seem to have violently seized prior to death should be submitted as a separate entry.
Factual error: Towards the end Ross pours wine on the egg sac to light it. Wine doesn't contain enough alcohol to ignite.
Suggested correction: He uses cognac and not wine, which is why it burns.
Revealing mistake: At the end when the dock 'kicks' the king spider off him into the fire, we hear it scream like a stuck pig. Then additional screams from the 'burning' spiders inside the pulsating nest, and when the doc torches both the king spider afterwards.
Suggested correction: Not sure how this is a mistake. Sure real world spiders don't making squealing noises but real world spiders also don't jump 30 feet or have venom potent enough to kill a human within seconds of being bitten.
It's a mistake because spiders cannot vocalize at all. The film creates a new spider species with exaggerated aspects of real life spiders: extremely potent venom, highly aggressive behavior, jumping ability, etc. What the film can't do is give the spiders traits they couldn't possibly have in real life.
Continuity mistake: After Becky's dad comes into the bathroom, and she screams, covering herself with the shower curtain, you can see her brother, who had died at the football game considerably earlier in the movie, through the bathroom's doorway, standing in the hall. It's only for a split-second, but as long as you're looking in the right spot, it's very clear.
Suggested correction: Not that what you said is wrong, but it actually makes sense. Metcalf was bitten by the original, non-bred spider. The other victims were bitten by spiders that were part house spider, part deadly spider. Therefore, the effects of the bites were different. I'm quite glad that I only had to see one gray, shriveled-up body.
Actually all three were bitten by hybrids.