Only slightly less classic than "Them!" "Tarantula" still manages to stand on its own as a strong entry in the Giant Bug movies of the 50s. Technically, its not a bug movie as tarantulas are arachnids and not insects, but movie-going audiences of the 50s didn't care. They just wanted to see big ugly bugs crushing everything in their path, and this film certainly delivers in that respect.
Taciturn scientist Leo G. Carroll is a man bent on finding a cure for world hunger. He invents a serum which enlarges whatever animal or insect (or arachnid) it is injected into. Unfortunately, when injected into a human, it causes acromegalia, a disorder marked by progressive enlargement of the head, face, hands, feet, and thorax, due to the excessive secretion of growth hormone. When one of Leo's human guinea pigs comes looking for revenge, he not only destroys the lab and injects the doctor with his own serum, but he shatters the glass cage of a puppy-sized tarantula, which quickly scurries out into the night.
Enter Mara Corday and John Agar. Mara Corday is the new lab assistant for Leo, and John Agar is the country doctor who takes an interest in the dark haired beauty. But there's not much time for romance as the tarantula, now roughly the size of the Goodyear blimp, begins terrorizing the desert. Farm animals are munched upon, and so too are human victims who are found in pools of venom, their bodies literally filled with enough poison to kill ten more men besides. Leo G. Carroll slowly turns into the Elephant Man, the giant spider peeks through the window at Mara in her nightie and Clint Eastwood shows up at films end to fire napalm at the eight legged menace.
Forget about "Earth vs. The Spider" and whatever you do, avoid "The Giant Spider Invasion" at all costs. This is the definitive Giant Spider film. It's smart and fast and well acted, and the spider itself is pretty cool looking, considering the fact that no furry robotic arachnids were constructed for this film, but instead film footage of a real tarantula was blown up and rear projected. It looks pretty good, considering the time. If you liked "Them!" you'll definitely want to check this one out as well.