IV.—PHENOMENA EXHIBITED BY THE LEPIDOPTERA. 19 
proportions. Experiments on some well-known varieties 
of HKuropean Moths have given like results, but in other 
cases no definite proportions have been obtained. From an 
evolutionary standpoint, Mendel’s Law is important, as 
it necessarily, to a great extent, prevents the swamping 
effects of interbreeding. In other words, if a useful variety 
arises, and is subject to Mendel’s Law, it will ultimately be 
fully reproduced in at least 25 per cent. of the offspring. 
We will now pass to the primary subject of this chap- 
ter and considera few of the more interesting and impor- 
tant phenomena, exhibited by Lepidoptera, and their inter- 
pretation by means of Natural Selection.* 
The close likenesses which the majority of Lepidopterous 
insects bear to inanimate objects is termed protective re- 
semblanee, and is, in fact, by far the most general method 
by which such small and defenceless creatures have con- 
trived to escape their numerous enemies. This class of pro- 
tection is very prevalent in New Zealand, as elsewhere, and 
has practically dominated the evolution of wing patterns 
and general coloration, in most of our native butterflies and 
moths. In the butterflies protective tints and patterns are 
chiefly confined to the under-surfaces of the wings, which 
alone are visible when the insect is resting. Examples of 
this class of protection are well shown in Vanessa gonerilla 
and V. itea, where the elaborate tracery of browns on 
the underside of the hind wings, gives the insect a deceptive 
resemblance to a dead leaf. The vivid yellow colouring of 
the underside of Chrysophanus salustius exactly imitates 
the colour of the dead or dying leaves of many of our 
native shrubs, and affords the butterfly most efficient protec- 
tion, when resting amongst foliage during wet or cloudy 
weather. In the moths protective patterns are chiefly con- 
fined to the upper surface of the forewings, but when both 
pairs of wings are exposed to view in repose, these patterns 
are present on the hind wings in addition. 
An attempt has been made, when dealing with each 
species, to explain, as far as possible, the protective value 
of both the wing patterns and the position assumed by the 
insect when at rest. The reader is therefore referred to 
subsequent chapters for further examples of protective 
resemblances, and it must here suffice-to state that the 
wing patterns of Lepidoptera are varied to assimilate with 
almost every conceivable environment, including such 
natural objects as bark, moss, dead leaves, lichens, bird- 
droppings, twigs, seeds, flower petals, ete., ete. 

*It is perhaps proper to mention here that attempts have 
been made, by some modern scientists, to discredit the explana- 
tion, by means of Natural Selection, of the phenomena briefly de- 
seribed in this chapter. In reply to such objectors, I would quote 
the following paragraph from! Professor Poulton’s address, de- 
livered to the Entomological Society of London, on 20th January, 
1926: “No reasonable hypothesis has ever been advanced on this 
subject except the one which assumes that the adaptive appear- 
ances of insects—protective resemblances, warning colours, mimi- 
cry (Batesian and Miillerian)—-have been gradually brought to 
a high pitch of perfection by selective destruction wrought by 
vertebrate enemies, above all by selection guided by the keen 
sight of birds.” 
It has been pointed out by Mr. A. H. Thayer that the 
protective resemblanees we observe in animals (including, 
of course, insects), are not produced by a mere approxima- 
tion in colour to surroundings, but that the general scheme 
of coloration is so arranged, that it has the effect of actu- 
ally effacing the animal, as a distinct object in the land- 
scape. For instance, the silver stripes on the underside of 
the hind-wings of Argyrophenga entipodum do not actually 
resemble blades of grass, but they exactly reproduce the 
light and shade effects present in a clump of grass, and thus 
efface the insect from view. The same effect is produced by 
the white streaks on the forewings of so many species of 
Crambus. Again, such vivid contrasts of colour, as those 
existing in Declana atronivea and D. egregia, as well as 
the vivid median bands, on the forewings of so many Geo- 
meters, break up, so to speak, the real outline of the insect, 
so that it no longer arrests the eye, as a distinct object 
apart from the general landscape. Mr. Thayer’s illumina- 
ting remarks, on the general question of protective resem- 
blanee, are due, no doubt, to his extensive artistic experi- 
ence, and must, I think, be regarded as one of the most 
important contributions to this branch of Natural History 
since the time of Darwin. Possibly the strongly contrasted 
light and dark bars on the legs of many species of Lepidop- 
tera prevent enemics from recognising their true nature 
and seizing hold of them. 
In rare instances we find species conspicuously or 
gaudily coloured, and these almost invariably have a nause- 
ous taste and are avoided by birds as unfit for food. Such 
species are said to be protected by warning colours, and it 
is obvious that unless a nauseous insect can be recognised 
before it is tasted, the possession of objectionable attributes 
would be of no benefit to it in the struggle for existence. 
Warning colours are, in fact, a protection against experi- 
mental tasting, as birds and other enemies soon learn to 
avoid any nauseous species which can be easily recognised. 
Warning colours are very common in the tropies but rarer 
in temperate regions. Danaida plexippus and Nyctemera 
annulata may be instaneed as good examples of warning 
colours amongst the New Zealand Lepidoptera. 
Conspicuous colours, temporarily displayed, often 
render the pursuit of an insect much more difficult than if 
the entire insect were protectively coloured. This is well 
shown in several species belonging to the genus Notoreas, 
which have the forewings coloured grey and closely resemb- 
ling rock surfaces, the hind wings being bright red, or 
orange. The momentary exhibition of the brilliant hind 
wings, when flying, makes it much more difficult for an 
enemy to locate the exact position of the insect, when it 
settles amongst the rocks. The protective tints of the fore- 
wings are then alone displayed, and the eye is unable to 
pick up a dull object, which has suddenly displaced a bril- 
liant one. 
The black coloration, characteristie of most Lepidop- 
tera inhabiting high alpine regions, has no doubt been ac- 
quired for the purpose of absorbing the heat of the sun, 

