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course be little, if any, doubt, that bees are capable of distinguishing colours; and I have proved experimentally that this is the case. Under these circumstances, I have been naturally anxious to ascertain, if possible, whether the same holds good with ants. I have, however, found more difficulty in doing so because, as shown in the observations just recorded, ants find their food so much. more by smell than by sight.

This being so, I could not apply to ants those tests which had been used in the case of bees. At length, however, it occurred to me that I might utilize the dislike which ants, when in their nests, have to light. Of course they have no such feeling when they are out in search of food; but if light is let in upon their nests, they at once hurry about in search of the darkest corners, and there they all congregate. If, for instance, I uncovered one of my nests and then placed an opaque substance over one portion, the ants invariably collected in the shaded part.

I procured, therefore, four similar strips of glass, coloured respectively green, yellow, red, and blue, or, rather, violet. The yellow was rather paler in shade, and that glass consequently rather more transparent than the green, which, again, was rather more transparent than the red or violet. I also procured some coloured solutions.

Prof. Dewar was kind enough to test my glasses and solutions with reference to their power of trans

mitting colour. Taking the wave-length of the ex treme visible red as 760 and that of the extreme violet as 397, we have

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The result of his examination of my glasses and solutions was as follows:

The light-yellow glass cut off the high end down to wave-length 442.

The dark-yellow glass cut off the high end down to wave-length 493.

The green glass cut off the high end down to wavelength 465, and also the red to 616.

The red glass cut off the high end down to wavelength 582.

The violet glass cut off the orange and yellow from wave-length 684 to 583, and a band between wave-lengths 543 and 516.

The purple glass cut off the high end down to wave-length 528.

The solution of chromate of potash cut off the high end to 507.

The saffron cut off the high end to about 473.

The blue fluid cut off the low end to 516.

The red fluid cut off the high end to 596.

I then (July 15, 1876) laid the strips of glass on one of my nests of Formica fusca, containing about 170 ants. These ants, as I knew by many previous observations, seek darkness, at least when in the nest, and would collect in the darkest part. I then, after counting the ants under each strip, moved the glasses, at intervals of about half an hour, so that each should by turns cover the same portion of the nest. The results were as follows-the numbers indicating the approximate numbers of ants under each glass (there were sometimes a few not under any of the strips of glass):

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Adding these numbers together, there were, in the twelve observations, under the red 890, under the green 544, under the yellow 495, and under the violet only 5. The difference between the red and the green is very striking, and would doubtless have been more so, but for the fact that when the colours were transposed the ants which had collected under the red sometimes remained quiet, as, for instance, in cases 7 and 8. Again, the difference between the green and yellow would have been still more marked but for the fact that the yellow always occupied the position last held by the red, while, on the other hand, the green had some advantage in coming next the violet. In considering the difference between the yellow and green, we must remember also that the green was decidedly more opaque than the yellow.

The case of the violet glass is more marked and more interesting. To our eyes the violet was as opaque as the red, more so than the green, and much more so than the yellow. Yet, as the numbers show, the ants

had scarcely any tendency to congregate under it. There were nearly as many under the same area of the uncovered portion of the nest as under that shaded by the violet glass.

Lasius flavus also showed a marked avoidance of the violet glass.

I then experimented in the same way with a nest of Formica fusca, in which there were some pupæ, which were generally collected in a single heap. I used glasses coloured dark yellow, dark green, light yellow, light green, red, violet, and dark purple. The colours were always in the preceding order, but, as before, their place over the nest was changed after every observation.

To our eyes the purple was almost black, the violet and dark green very dark and quite opaque; the pupa could be dimly seen through the red, rather more clearly through the dark yellow and light green, while the light yellow were almost transparent. There were about 50 pupæ, and the light was the ordinary diffused daylight of summer.

These observations showed a marked preference for the greens and yellows. The pupa were 6 times under dark green, 3 under dark yellow, 34 under red, and once each under light yellow and light green, the violet and purple being altogether neglected.

I now tried the same ants under the same colours, but in the sun; and placed a shallow dish containing some 10 per cent. solution of alum sometimes over

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