Which of the following is NOT a characteristic of insects from the Order Diptera?

Insects from the Order Diptera are indeed characterized by possessing two wings, experiencing complete metamorphosis, and having distinct larval stages. The correct identification of the characteristic that is not applicable to them is the term "true bugs," which is commonly used to refer to insects in the Order Hemiptera, not Diptera.

Insects in the Order Diptera include flies and mosquitoes, which are recognized by their unique structure of having a single pair of wings for flying, while the other pair typically has evolved into stabilizers called halteres. Complete metamorphosis is also a critical life cycle trait for Diptera, involving distinct larval stages (often referred to as maggots) that are different from the adult form. Therefore, associating Diptera with "true bugs" would be incorrect, as that term specifically refers to a different group of insects altogether.