Tarantula (movie, 1955)

A lone-wolf scientist sequestered in a mansion near a small desert town arouses the suspicion of the town's doctor when his lab assistant is found dead from a case of acromegaly which took only four days to develop. As the doctor investigates, aided by the scientist's new, and very female, assistant, they discover that, far worse, something much larger and hungrier than it ever should be, is devouring local cattle - and humans - in increasingly large quantities.