Final answer:
The defence mechanism where inchworms look like twigs is known as camouflage.
Step-by-step explanation:
The defence mechanism where inchworms look exactly like twigs in their shape and colour is known as camouflage. Camouflage is used by many species to avoid being detected by predators. The tropical walking stick insect and the chameleon are other examples of organisms that use their body shape and coloration to blend in with their surroundings and avoid detection.