




20 IV.—PHENOMENA EXHIBITED BY THE LEPIDOPTERA. 
during the transient periods of intensely hot sunshine which 
oceur in such localities. The same class of colouring also 
prevails amongst species found in high latitudes. Lord 
Walsingham, who first drew attention to these adaptations, 
made some very interesting experiments by placing a black 
and white insect on snow, and observing the relative rate 
at which each sank when exposed to the sun’s rays. It was 
found in every ease that the black insect made a much more 
rapid impression on the snow than the white one, owing 
to its superior absorptive powers. It is clear that in a cold 
and stormy climate, like that existing in alpine or sub- 
aretie regions, the black insect, which matured rapidly, 
and was able to pair and deposit its eggs in the shortest 
possible time, would have a distinct, advantage in the 
struggle for existence over the more slowly developing 
white insect, which, owing to its inability to rapidly absorb 
heat, could not fully avail itself of such short periods of 
hot sunshine. A less pronounced melanism, or tendency to 
dark coloration, is often observed in Lepidoptera found in 
very damp localities, and many species, which in their 
markings imitate moss and lichens, are more vividly 
coloured in wet than in dry localities. This is, I think, 
due to the darkening of the tree-trunks, and the more 
luxuriant growth of lichens and mosses indueed by an 
almost constant and heavy rainfall, the protective colour- 
ing of the moths being correspondingly modified to meet 
the special environment. These conditions are, in fact, ful- 
filled on the West Coast and in the extreme South of New 
Zealand. <A similar darkening has been observed amongst 
Lepidoptera taken near the great manufacturing towns in 
England, where the tree-trunks are darkened by deposits 
of smoke, the colouring of the moths having also darkened 
in order to afford them the needful protection. It is obvious 
that a light-coloured insect on a dark tree-trunk would be 
at once detected and destroyed, and that the darker forms 
alone would survive. 
Certain special markings near the extremities of the 
wings, in some species of butterflies and moths, are prob- 
ably not merely ornamental, but subserve a useful purpose 
by inducing an enemy to seize a non-vital part of the 
insect, the victim thus escaping with the loss of an insignifi- 
cant portion of its wing. The eye-like mark on the short 
tail of the hind wing of Dodonidia helmsi is probably a 
special marking of this kind as, when the butterfly is rest- 
ing, it roughly suggests the insect’s head, the real head, of 
course, being in a very different position. In several 
species, belonging to the genus Hrechthias and its allies, 
the real head is extremely small, but the apical portion of 
the fore-wings is bent over and ornamented with an eye- 
like marking. This causes the posterior extremity of the 
resting insect to bear the closest possible resemblance to a 
head but, in the event of an enemy seizing this spurious 
head, the little moth would inevitably escape with the loss 
of the tips of its fore-wings. Many similar special markings 
have been observed, especially in tropical butterflies, and 
in this connection a careful study of all specimens, whose 
wings have been mutilated under natural conditions, is 
very desirable, and might lead to the discovery of the uses 
of many wing-markings which are at present unknown. 
In the ease of butterflies frequenting hot, arid localities, 
the shadow of the insect is often more conspicuous than 
the creature itself, and any reduction in the size of the 
shadow would be beneficial in helping the butterfly to 
escape detection by its enemies. Many observations appear 
to indicate an instinctive habit amongst some butterflies to 
incline their wings at such an angle to the sun as to re- 
duce the shadow to a minimum. Further investigations 
are required on this interesting subject, and might be pur- 
sued with advantage in connection with several of our New 
Zealand species. 
The habit followed by many larvae of lowering them- 
selves from the branches of trees into mid-air, whilst sus- 
pended by a silken thread, and ascending to their original 
position when the danger is past, has no doubt proved a 
useful expedient in enabling the insect to avoid destruction 
by birds. I have also seen a larva escape from the attack 
of an ichneumon fly by the same method. 
In New Zealand it has been observed that in the 
majority of cases Lepidoptera emerge from the pupa two 
or three hours after sunset. Hence the process of expand- 
ing and drying the wings is completed during the hours of 
darkness, and the insect is fully matured and ready for 
flight before day-break. It is probable that this habit has 
been acquired through Natural Selection as it is obvious 
that the soft, newly emerged, helpless imago would, if 
visible in full daylight, fall a very easy victim to birds. No 
protective colouring for its concealment is available before 
the wings themselves are fully expanded and sufficiently 
rigid to assume a natural position, neither can the newly 
emerged insect escape from an enemy by flight. It would 
thus appear that emergence early in the night, affords the 
species an easy method of avoiding the manifold dangers 
which beset it during the initial period of imago life. I am 
indebted to Mr. R. M. Sunley for directing my attention to 
this interesting subject. 
For the superficial resemblances, which frequently 
exist between insects having no real relationship, the term 
Mimicry is used. This is a much more subtle means of pro- 
tection than any previously considered, and on this ac- 
count its real significance is still sometimes doubted. In 
the most simple cases of mimicry we find a harmless, edible, 
or defenceless species, closely resembling another species 
having a nauseous taste, or armed with a sting, or some 
other effective weapon of defence. Simple mimicry of this 
description is called Batesian Mimicry from its discoverer 
H. W. Bates. Its origin can be traced to the operation of 
natural selection, as it is clearly an advantage for a harm- 
less insect to resemble one, either possessing a nauseous taste, 
or armed with a sting, and any variations tending in such 
a direction would be continually improved, through the 
preservation of those forms, which most closely approxi- 
mated, in general appearance, to the specially protected 

