Revealing mistake: When the scientists inject the mouse with poison, they put it in a jar. The, after they place it down you can see someone's hand swap the jar for one containing a dead mouse. You can even hear it. (01:17:58)
Revealing mistake: When Becky sees the spider in the shower, there are two instances when you can see the bodystocking she's wearing, covering her breasts, to preserve her modesty, most noticeable when she screams. (01:11:53)
Revealing mistake: When Jerry Manley gets bitten by the spider in the tent in South America, the others come to look at his corpse, you can see clearly see his neck pulsating, when he should be dead. (00:15:35)
Revealing mistake: When Becky gets out of the shower naked, her father walks in on her and you can clearly see her wearing pants, reflected in the mirror, to keep her modesty. (01:10:05)
Revealing mistake: In the scene where Dr. Ross Jennings is trapped in the corner of the cellar, you can see that the tarantula which starts climbing up his leg has a huge black stick stuck to the back of its body, pushing it along. (01:36:05)
Revealing mistake: When the flaming "general" spider is killed, there's several mistakes. When it leaps, it suddenly "freezes" in mid-air for a second before the nail hits it. Then, when we see the nail hit it, you can see a wire attached to it, plain as day, to yank it back. Then, when it hits the egg-sack, you can see several fake spiders attached to it, which don't move at all. Then the egg sack catches on fire, but the flames come from behind the sack, even though the general hit the front.
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.
Revealing mistake: When the General is lowering himself towards Jennings on a string of web, there's a couple of shots where the spider is completely immobile, revealing the spider to be a prop. Most noticeable just before Jennings smacks him with a wine bottle.
Revealing mistake: When Atherton is using his fog machine to spray up into the tree look to his left, you can see another spray of the fog being added to the tree by an unseen stagehand.
Revealing mistake: When Margaret (the blood pressure lady?) gets settled for the night, one of the baby spiders is crawling toward the couch where she's sitting. In the very next shot that same spider is suddenly 'hiding' inside the lampshade above her and bites her.
Revealing mistake: Near the end it is way obvious that the king spider is animatronic as it goes for the doctor, considering it's tech string is quite visible in the closeup. And it "hisses" as it's lowered.
Revealing mistake: Two very different types of spiders are used in most of the shots. In the closeups they are larger, with bulbous legs, defined hairs, and big eyes.
