The Wasp Woman

This 1960 Roger Corman film was no doubt designed to cash in on the success of 1959's The Fly. Susan Cabot plays the owner of a cosmetic company. The company is based on her image, but she is getting older. She discovers a scientists who has somehow created a youth serum made from the enzymes from the jelly of a queen wasp. She begins to take this enzyme treatment, and at first it seems to be working. But she grows impatient and she secretly gives herself a big injection of the formula and --here's the part you never would have guessed in a million years-- she starts turning into a wasp! She begins to dispatch her victims in quite a bloody manner for 1960.
(The Wasp Woman actually has the head and hands of a wasp but the body of a woman -- exactly the opposite of the image on the poster. But I digress.)
If you seen Corman's Little Shop of Horrors, you know what to expect in terms of quality. Yeah, it's cheap, but what what little money that was spent was spent well.
This film did wonders for Susan Cabot's career -- she didn't work again for ten years.