Panther Girl of the Kongo.

Jean Evans of an international wildlife foundation, who is known to Africa as 'the Panther Girl' because of her bravery in jungle living, stumbles on a plot by a mad scientist to frighten the natives out of a diamond-laden district by chemically growing crayfish to giant size, and enlists the aid of a game hunter friend to prevent a monster rampage and bring the culprits to justice.