Solinus, whose work, _Polyhistor_, is mainly a compilation from Pliny's Natural History, gives a similar account of the swarms of winged serpents about the Arabian marshes, and states that their bite was so deadly that death followed the bite before pain could be felt; he also refers to their destruction by the ibises, and is probably only quoting other authors rather than speaking of his own knowledge. Cicero, again, speaks of the ibis as being a very large bird, with strong legs, and a horny long beak, which destroys a great number of serpents, and keeps Egypt free from pestilential diseases, by killing and devouring the flying serpents, brought from the deserts of Lybia by the south-west wind, and so preventing the mischief which might attend their biting while alive, or from any infection when dead. There are not unfrequent allusions in ancient history to serpents having become so numerous as to constitute a perfect plague; the dreadful mortality caused among the Israelites by the fiery serpents spoken of in Numbers is a case in point, and another[189] is the migration of the Neuri from their own country into that of the Budini, one generation before the attack of Darius, in consequence of the incursion of a huge multitude of serpents. It is stated that some of these were produced in their own country, but for the most part they came in from the deserts of the north. The home of the Neuri appears to have been to the north-west of the Pontus Euxinus, pretty much in the position of Poland, and I believe that at the present day the only harmful reptile occurring in it is the viper common to the rest of Europe. Diodorus Siculus[190] mentions a tradition that the Cerastes had once made an irruption into Egypt in such numbers as to have depopulated a great portion of the inhabited districts. These stories are interesting as showing a migratory instinct occurring in certain serpents, either periodically or occasionally, and are thus to some extent corroborative of the account of the annual invasion of Egypt by serpents, referred to in a previous page. They also, I think, confirm the impression that serpents were more numerous in the days of early history, and had a larger area of distribution than they have now, and that possibly some species, such as the Arabian and flying serpents, which have since become extinct, then existed. Thus the boa is spoken of by Pliny as occurring commonly in Italy, and growing to such a vast size that a child was found entire in one of them, which was killed on the Vatican Hill during the reign of the Emperor Claudius. Yet at the present day there are no snakes existing there at all corresponding to this description.