In some groups of insects, the mesonotum is hypertrophied, such as in Diptera, Hymenoptera, and Lepidoptera), in which the anterior portion of the mesonotum (called the mesoscutum, or simply "scutum") forms most of the dorsal surface of the thorax.
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In Diptera and Hymenoptera the mesothoracic scutellum is also distinct, but much smaller than the mesoscutum.