Lewis & Short

insomnĭa, ae, f. (plur. insomnia, n., Plin. 20, 9, 33, § 82; Prop. 2, 25, 47; Val. Fl. 1, 329; 7, 6; 2, 140) [insomnis], sleeplessness, want of sleep (class.): consequitur comes insomnia, Caecil. ap. Non. 209, 15: aut mox noctu te adiget horsum insomnia, Ter. Eun. 2, 1, 13 Fleck. (Umpfenbach, adigent, v. insomnium): incitabatur insomnia, Suet. Cal. 50.
In plur.: neque insomniis, neque labore fatigari, Sall. C. 27, 2: insomniis carere, Cic. de Sen. 13, 44.