Robigo means red rust or mildew which attacks cereals when the ear is beginning to be formed[309], and which is better known and more dreaded on the continent than with us. This destructive disease is not caused by the sun’s heat, as Pliny[310] tells us was the notion of some Italians, but by damp acting in conjunction with a certain height of temperature, as Pliny himself in fact explains it. Robigus[311] is the spirit who works in the mildew; and it has been conjectured that he was a form or indigitation of Mars[312], since Tertullian tells us that ‘Marti et Robigini Numa ludos instituit’[313]. This is quite consistent with all we know of the Mars of the farm-worship, who is invoked to avert evil simply because he can be the creator of it[314]. The same feature is found in the worship of Apollo, who had at Rhodes the cult-title ἐρυθίβιος[315], or Apollo of the blight, as elsewhere he is Apollo Smintheus, i. e. the power that can bring and also avert the pest of field-mice. Robigus had a grove of his own at the fifth milestone on the Via Claudia; and Ovid relates in pretty verses how, as he was returning from Nomentum (doubtless by way of his own gardens, which were at the junction of the Via Claudia with the Via Flaminia near the Milvian bridge[316]), he met the Flamen Quirinalis with the _exta_ of a dog and a sheep to offer to the god[317]. He joined the procession, which was apparently something quite new to him, and witnessed the ceremony, noting the _meri patera_, the _turis acerra_, and the rough linen napkin[318], at the priest’s right hand. He versified the prayer which he heard, and which is not unlike that which Cato directs the husbandman to address to Mars in the lustration of the farm[319]: Aspera Robigo, parcas Cerialibus herbis, Et tremat in summa leve cacumen humo. Tu sata sideribus caeli nutrita secundi Crescere, dum fiant falcibus apta, sinas. Parce, precor, scabrasque manus a messibus aufer, Neve noce cultis: posse nocere sat est, &c. Ovid then asked the flamen why a dog—_nova victima_—was sacrificed, and was told that the dangerous Dog-star was in the ascendant[320]: Est Canis, Icarium dicunt, quo sidere moto Tosta sitit tellus, praecipiturque seges. Pro cane sidereo canis hic imponitur arae, Et quare pereat, nil nisi nomen habet. In this, however, both he and the priest were certainly mistaken. Sirius does not rise, but disappears on April 25, at sunset; and it is almost certain that the sacrifice of the dog had nothing to do with the star. The real meaning of the choice of victim was unknown both to priest and poet: but modern research has made a reasonable attempt to recover it[321].