930 Marvels of the Universe 
THE LEG OF A MOTH. 
Notice the long silky hairs fringing the upper part of the leg 
and the thick woolly scales covering the leg itself. 
teen times.) 
(Magnified six- 
The colours are produced by two methods, 
the brilliant metallic effects are due to 
iridescence, and the sombre hues largely to 
the presence of pigment contained in the 
scale. As previously stated, the scales, 
although so minute, have a complex struc- 
ture ; indeed, they were formerly much used 
as test-objects for microscope lenses. Not 
only are they very variable in form, but 
they are also delicately marked with fine 
strie, or lines, rows of bead-like dots, and 
other markings which to resolve test the 
powers of the best lenses. 
Sometimes they are slightly undulated or 
irregular, and this structural detail, together 
with their line-like markings, produces the 
iridescent colour-changes seen on the wings 
of many butterflies. The lines and curved 
parts of the scale cause a shadow to fall in 
a greater or less degree on the opposite side 
to that of the source of light ; and so with 
every movement of the insect the rays of 
light are caught at different angles, causing 
refraction, and consequently giving origin 
to a variety of colours—just as a glistening 
diamond does. 
Some of the Morpho Butterflies of tropical 
America are the most dazzling and beautiful 
objects in the insect world. Their wings, 
when expanded, extend from six to seven 
inches, presenting lovely iridescent sheets 
of the palest blues to the sunlight, which at 
the slightest movement suddenly change into 
deep blues and purples. It is said that on 
the Amazons the flashing of the wings of 
these insects can be seen half a mile away, 
giving the effect of small mirrors catching 
and reflecting the sunlight. 
It has been calculated that on the wings 
of a butterfly of the genus Morpho there 
are arranged no less than a million and a 
half of these light-refracting scales ; some 
butterflies have no fewer than one hundred 
thousand to the square inch. 
The males of many species of butter- 
flies have, in addition to the ordinary 
scales, some of special form, which are 
known as plumules. These scales are 
not infrequently of a battledore shape, 
