What is the outermost layer of cells of an insect's exoskeleton called?

The outermost layer of cells of an insect's exoskeleton is referred to as the cuticle. This structure serves as a protective barrier for the insect, providing strength and preventing water loss. The cuticle is composed of various layers, including the epicuticle, exocuticle, and endocuticle, and it plays a crucial role in the insect’s overall physiology and protection.

While sclerites refer to hardened plates of exoskeleton contributing to the structure, and chitin is a key biochemical component of the cuticle itself, the term "cuticle" specifically encompasses the entire outer layer of the exoskeleton, making it the most accurate answer to the question about the outermost layer of an insect's exoskeleton. The exocuticle is a layer beneath the epicuticle and is part of the cuticular structure, but it is not the outermost layer. Thus, understanding these distinctions clarifies why the cuticle is the correct answer.