scutum
From ZooTerms (Dictionary of Invertebrate Zoology)
horny or chitinous plate.
scutum (noun; plural scuta; Latin scutum, shield): 1. Any long,
2. (Arthropoda: Chelicerata) In Acari, the large, anteriodorsal sclerite.
3. (Arthropoda: Crustacea) In thoracic barnacles, a paired plate or valve. a. In Lepadomorpha, one on each side of the occludent margin of the capitulum. b. In Verrucomorpha, a fixed scutum, one of 4 principal plates, and a movable scutum, 1 of 2 opercular plates. c. In Balanomorpha, one of 4 opercular plates.
4. (Arthropoda: Insecta) The middle division of the thoracic notum, anterior to the scutellum. a. In Hymenoptera, the major part of the dorsum of the mesothorax in winged Formicidae. b. In Diptera, sometimes referred to as the eunotum.
5. (Bryozoa: Gymnolaemata) In anascan Cheilostomata, a broad, flat, lateral, marginal spine overhanging the frontal area.