What is the name of the structure located behind an insect's head that covers part of the head and mesothorax?

The structure located behind an insect's head that covers part of the head and mesothorax is known as the pronotum. The pronotum is a plate-like structure that forms the dorsal part of the prothorax (the first segment of the thorax) and is typically more pronounced in certain insect groups, such as beetles and grasshoppers. Its primary function includes offering protection to the head and contributing to the overall structure and mobility of the insect.

The prothorax refers to the segment of the thorax that is immediately behind the head and includes the pronotum as part of its anatomy. The head capsule is specifically the hardened structure that houses the insect's mouthparts and eyes, but it does not extend behind the head as the pronotum does. Thorax shield is not a recognized term in entomology, making it less relevant in this context. Therefore, the pronotum is the most accurate term to denote the structure described in the question.