Page:Popular Science Monthly Volume 19.djvu/512

496 described other species of ants (genus Atta) as fond of light. It would be interesting for any one who has an opportunity to try whether ants of this genus do not show toward the rays of the spectrum a scale of preference the reverse of that which Sir John Lubbock described.

As regards hearing, Sir John found that sounds of various kinds do not produce any effect upon the insects, nor could he obtain any evidence of their emitting sounds, either audible or inaudible to human ears.

It has long been known that the sense of smell in ants is highly developed, and it appears to be the sense on which, like dogs, they mainly rely. Huber proved that they track one another's footsteps in finding their way to food, etc.; for he observed, on drawing his finger across the trail so as to obliterate the scent, that the ants became confused and ran about in various directions, till they again came upon the trail on the other side of the interrupted space. By many ingeniously devised experiments Lubbock has amply confirmed Huber's statements, and concludes that in finding treasure "they are guided in some cases by sight, while in others they track one another by scent"—depending, however, more upon scent than upon sight.

There can be little doubt that ants have a sense of taste, as they are so well able to distinguish sugary substances; and it is unquestionable that in their antennæ they possess highly elaborated organs of touch.

—It is certain that ants, in common with many other animals, possess some unaccountable sense of direction, whereby they are able to find their way independently of landmarks, etc. Sir John Lubbock tried a number of experiments in this connection, of which the following is perhaps the most conclusive: Between the nest and the food he placed a hat-box, in each of two opposite sides of which he bored a small hole, so that the ants, in passing from the nest to the food and back again, had to go in at one hole and out at the other. The box was fixed upon a pivot, where it could be easily rotated, and, when the ants had well learned their way to the food through the box, the latter was turned half round as soon as an ant had entered it; "but in every case the ant turned too, thus retaining her direction."

Sir John then placed in the stead of a hat-box a disk of white paper. When an ant was on the disk making toward the food, he gently drew the paper to the other side of the food, so that the ant was conveyed by the moving surface in the same direction as that in which she was going, but beyond the point to which she intended to go. Under these circumstances the ant did not turn round, but went on to the farther edge of the disk, "when she seemed a good deal surprised at finding where she was."

These results seem to indicate that the sense of direction is due to a process of registering all the changes of direction which may be