The erratic migrations of certain insects, often in countless swarms, have been noticed and put on record by many observers. In a country where, perhaps, they are scarce, or, it may be, almost wanting ordinarily, they may suddenly put in an appearance in such numbers as to defy all attempts at computation; or immense swarms of them may sometimes be seen far out at sea, flying steadily in a direction which may take them out so far as to effectually prevent any return.