@MarlonDark mealworm coloration, uncanny resemblance to molitor adults (striated elytra, somewhat elongated shape, ridged round pronotum with pointy edges), and ability to survive in dry grains are all traits consistent with Tenebrio obscurus. I do not know any other darkling with this exact trait combination so obscurus seems very probable.
@Hisserdude, can you confirm or deny my ID?