Which is a characteristic of all adult insects?

All adult insects possess three distinct body regions: the head, the thorax, and the abdomen. This characteristic structure is fundamental to the anatomy of insects and is used to identify them as part of the class Insecta. Additionally, insects are characterized by having six legs, which is a defining feature of their body plan. The combination of three body regions and six legs is essential for the classification of an organism as an insect, making this answer accurate and reflective of the biological classification system.

Insects have evolved to exhibit this three-part body structure and a hexapod (six-legged) design, allowing them to adapt to a wide range of environments and lifestyles. This consistency across adult insects is critical for entomologists and anyone involved in pest management, as it aids in identification and understanding of insect behavior and physiology.