Entom. Pl. -ia. [f. Gr. type *θυρίδιον, dim. of θῠρίς, θυριδ- window, opening.] A whitish spot on the fore-wing of Trichoptera, marking a break in the cubital vein; also applied to similar spots occurring on the wing veins of some other insects.
1861. Hagen, Synopsis Neuropt. N. Amer., 259. Thyridium and first subapical areole with a whitish spot.
