Which of the following is NOT one of the three body regions of insects?

Insects are organized into three distinct body regions: the head, thorax, and abdomen. Each region serves specific functions essential for the insect's survival and interaction with its environment. The head contains sensory organs and mouthparts essential for feeding, the thorax is responsible for locomotion as it houses the legs and wings, and the abdomen contains digestive and reproductive organs.

The option relating to "Pelvis" is not relevant in the context of insect anatomy. Insects do not have a pelvic region as part of their body structure. The term "pelvis" typically refers to a part of the skeletal system in vertebrates, which is not applicable to the body plan of insects. By understanding these primary regions, it becomes clear why the "pelvis" is not included among the body regions of insects.