94 REV. F. A. WALKER, D.D., F.L.S., 
even if there be no rain, will all in a moment disappear, and 
where they betake themselves is equally past finding out. 
One’s own shadow projected across a flower or leaf on which 
an insect is settled, without the slightest noise, will cause it 
rapidly to take wing, so dependent is it for its brief hour of 
enjoyment on the sun’s brightness. Although, as I just now 
said, it becomes no brighter for many days of sunlight, it does 
become considerably faded in some instances between the 
beginning and end of the season. Observe a specimen of a 
painted lady butterfly that has successfully hybernated, and 
reappeared in the ensuing spring, and look at the difference 
that those humble bees ordinarily known as red tails (Bombus 
lapidarius, for example) show between spring and autumn and 
the period when they are found on the early blossoms of the 
dead nettle and the time when they haunt the flowers of the 
late lingering thistles,—in the former instance bright orange, 
and in the latter a dull rust colour. Again, birds, fishes, and 
insects have been correctly said to alone possess the metallic 
colour; while plants and zoophytes are without reflecting 
shades, and the mollusea to take a middle path with their hue 
of mother-of-pearl. But in any inquiry,—so far as inquiry 
can be made,—into the causes to which animal colouring is 
due, we must be careful to distinguish between three sorts of 
colour, which I will venture to term for convenience’ sake uni- 
form, metallic, and iridescent, and then to convey my meaning 
with regard to these three appellations. 
Uniform, such as all butterflies possess, and which is evident 
to the most superficial observer, and seen even under a dull 
light, as for example the yellow of the sulphur, the crimson 
and blue of the peacock, the scarlet, black, and white of the 
red admiral. 
Metallic, peculiar to certain tribes of birds and butterflies 
like humming-birds and morphos. In the case of Morpho 
cypris, for example, it is a shifting tint, for as that resplendent 
insect is viewed flat in a drawer, now one side appears bright 
blue, and now again the other, while the left or right wing 
alternately seems dark. The drawer requires to be held up 
and turned to and fro under a full, strong light, for the 
beauties of insects of this description to be thvroughly 
realised. It is noteworthy to observe with regard to another 
species of this group, Morpho sulkowskii, and its metallic 
tint, that it has the same markings in consequence, though 
not the same tint on both upper and under surface, owing to 
its wings being very transparent, presumably from the coating 
of scales being very thin, and that the pencilled markings on 
