Marvels of the Universe 923 
that of an insect that any comparison 
is almost useless. He, however, at least 
knows that while his own two eyes 
each take up an image, yet only one 
picture is conveyed to his brain. Pro- 
bably the Swallow-tail Butterfly, with 
eye-facets estimated in round figures 
at seventeen thousand in each eye- 
mass, and the Death’s-head Moth, 
whose lenses likewise number about 
twelve thousand, both view the ob- 
jects around them much as we ourselves 
do, or it may be that their different 
visual organs give them an understand- 
ing of form and colour that to us would 
be incomprehensible. The matter is 
0 PAA wate Wail 
still more complicated from the fact 
that moths, in addition to their com- 
pound eyes, often possess on the sum- 
mit of the head ocelli, or single eyes. 
When they are present, there are Photo by] LE. J. Spitta, F.R.M.S. 
two, but sometimes they are absent. THE TONGUE OF A MOTH. 
Furthermore, in butterflies these single The scale of magnification is much larger than in the preceding 
: 2 photograph, and the little tubes which project from the tissues of 
eyes are entirely wanting. the tongse can be easily seen. These tubes are probably taste 
As most of the higher forms of in- organs, as are also the leaf-shaped excrescences clustered together at 
a the tip of the tongue. 
sects possess ocelli, as well as com- 
pound eyes, it would seem that these single eyes have entirely lost their function and dis- 
appeared in the butterflies, and are now following the same course in the moths. Probably the 
feathery scales which clothe the heads of these insects may have played some part in their 
suppression by obscuring the light from them. 
In spite of their extraordinary visual organs, there is no striking evidence to show that either 
butterflies or moths possess very keen sight. I am inclined to think that their power of distin- 
guishing colour is much greater than that of recognizing form. The other day I was much interested 
in watching the familiar small white butterflies amongst some sweet-peas in my garden. Only a 
few flowers were blooming, and their colours were white, pink and purple. While watching for 
over an hour, I found that nearly every small white butterfly which flew near was attracted towards 
the few white flowers; and, as they do not attempt to sip nectar from the blooms, but imme- 
diately fly off again on reaching the flower, I could only assume that they mistook the flowers for 
others of their species, and had to approach closely before discovering their mistake. It was a 
significant fact that not a single one visited either the pink or purple flowers. 
Then there is the behaviour of moths and other insects before a bright light, especially in the 
case of some of the hawk-moths, which sometimes become so reckless as to plunge at the globes of 
electric arc-lights with such force as to cause them to be hurled stunned and helpless to the ground 
—a fact which seems to show that their sight-organs differ from our own. It is remarkable, too, 
that some moths are never attracted by light. In explanation of this, I would suggest that a bright 
light probably presents to the eye of an insect a succession of rapid waves, or perhaps vortex move- 
ments, which exert on it a fascination very similar to that which a large, revolving flywheel of an 
engine, or even the continually rippling waves on the surface of water, does on many sensitive 
people. Just as there are people who can coolly face these things without losing control of their 
67 
