Vacca was the author of a well-known commentary on Lucan’s Bellum Civile that was used frequently in later eras.  His authority equaled that of other famous commentators (e.g. Servius, Priscian, and Isidore), and reference to him required no further explanation.  Some identify him with the commentator on Lucan mentioned by Jerome (Adv. Ruf. 1.16).  It was recognized over a century ago that both the Commenta Bernensia [see card] and the Adnotationes super Lucanum [see card] are in part derived from his commentary (Genthe 1872; Endt 1909), and despite some skepticism by Ussani (1911), a few decades later Marti (1950) leveled strong arguments that confirmed the thesis.  Weber (1821) also attributed to Vacca the Vita Lucani preserved in some manuscripts transmitting the scholia, but this thesis has since been refuted (Ussani 1903; Marti 1950; Martina 1984).  There is great uncertainty concerning the period in which Vacca lived; nevertheless, the facts that Isidore of Seville is never cited in the glosses attributed to Vacca and that some of the lost books of Livy survive in these fragments suggest a dating prior to the 6^th c., perhaps the 4^th or 5^th (Weber, Genthe, Helm, Paratore).  Rostagni maintains that it can be dated to a period only slightly later than Lucan himself.  Numerous authors cite Vacca as an authoritative source, including Anselm of Leon (11^th-12^th c.) and Petrarch; this would seem to suggest that a copy of Vacca’s commentary was perhaps still available during their lifetimes.  It has been hypothesized that Vacca was a native of Liguria—or less probably of Italy—on the basis of a curious gloss attributed to him in the codices, in which Lake Léman is located prope Liguriam (Marti).  Rostagni maintains, on the other hand, that the commentator could have been Spanish: in describing Lucan’s fatherland as honored by the poet, Vacca says that there was a people in Spain called ‘Vaccaei’ and that a river in Lusitania was called ‘Vacca’ or ‘Vacua’. [R. Tabacco; tr. C. L. Caterine].