Art. XXXV.—Observations on the Occurrence of a Butterfly, new to New Zealand, of the Genus Danais.
[Read before the Philosophical Institute of Canterbury, 2nd January, 1874.]
In February last I had the pleasure of receiving from my friend, Mr. F. H. Meinertzhagen, of Waimarama, Hawke Bay, a large handsome butterfly of the genus Danais, captured by him at Waimarama on the 31st January last.
Upon comparison the species appears to be identical with that of a New South Wales specimen of Danais, in the Canterbury Museum, received from Mr. C. French, of the Botanical Gardens, Melbourne, and labelled by him “Danais erippus, N.S.W., supposed to have been introduced. Common Indian and American species.”
There is also another specimen of Danais in the Canterbury Museum, amongst a collection of Californian Lepidoptera, received from Mr. Edwards, of San Francisco, and labelled by him Danias archippus; and that and the New South Wales and New Zealand species are so alike, that I fail to distinguish any specific difference. That there is a difference between erippus and archippus we have the authority of Mr. Butler, who had the typical specimens to refer to, and has placed the species apart in the Catalogue (recently prepared by him) of Diurnal Lepidoptera, described by Fabricius, in the collection of the British Museum; but what the difference is does not appear from the short descriptions of Fabricius and Cramer, quoted by him, and I have no other description to guide me.
I do not find, either in Mr. Butler's Catalogue, or in the Encyclopèdie D'Histoire Naturelle par le Dr. Chenu (the only authorities at hand to refer to), any mention of erippus occurring in America, and perhaps Mr. French may have been led to note its being common in America from having compared a specimen of the New South Wales species with a Californian specimen, similar to that in the Canterbury Museum, and failed, as I have, to discover any difference between them.
Assuming that the New South Wales and American specimens are distinct species, I prefer to treat the New Zealand species as identical with that of New South Wales, and adopt the specific name of berenice instead of erippus—the Fabrician specific name erippus having given place to that of berenice, Cramer. (See Butler's Cat. Diur. Lep., p. 4.)
From Dr. Hector I have also received a specimen of this butterfly, taken last summer at Hokitika, where he saw it in great abundance; and, since the capture of the first, Mr. Meinertzhagen has taken several more specimens at Waimarama, and to him I am indebted for the pains he has taken in obtaining for me much valuable information respecting the insect.
He informs me that whenever he has seen the butterfly it has been flying high, but not swiftly, in sunny sheltered places among trees, and settling on them. He also saw it travelling fast over the country along the coast. The first he saw early in November, and the last he took the first week in April. All the Maoris to whom he showed the butterfly said they knew it, and the old Maoris say it is called “kãkãhũ,” and is in some years very plentiful. The caterpillar, they tell him, was very plentiful this year, and feeds upon the pollen of the gourd which they grow in that part of the country (Hawke Bay). They are unanimous in saying that the butterfly was there before any white man came, and the Rev. W. Colenso, of Hawke Bay, told Mr. Meinertzhagen that he saw it there many years ago.
Having heard that his neighbour, Mr. Nairn, had been feeding some newkind of caterpillar found in his garden, Mr. Meinertzhagen wrote to him and obtained three pupæ, which he describes as short and stumpy, of a pale green colour, and dotted with gold spots on the edge of the part which covers the wings. The Maori to whom he showed them recognized them as the pupæ of the Danais. Unfortunately the rats got at and destroyed them.
Mr. Nairn sent him a coloured sketch of the caterpillar, and said he had made the sketch entirely from memory and was unable to give the exact proportions of the caterpillar or its number of legs; that it had two horns or feelers on its head, and they appeared to be in continual motion. He describes the shrub on which he found the caterpillar as the Gomphocarpus ovata, one of the milk-producing plants, and a native of the Cape of Good Hope. The caterpillar is represented in the drawing as black, with the joints of the segments yellow, and some white spots on the head and second segment. Two rather long tentacles or appendages appear to rise and project from the second segment or back part of the head, and a caudal horn from the last segment.
I am not aware of any record of this species of butterfly having been captured before in New Zealand, but, as I have already stated, the Hawke Bay Maoris and Mr. Colenso testify to its appearance in former years.
That the butterfly has been “introduced” into New Zealand, or even into New South Wales (as intimated by Mr. French), seems to me extremely improbable.
If introduced it must have been either purposely or accidentally. That it has been purposely introduced I think no one will credit without some record of such introduction. That it has been accidentally introduced I think equally improbable, and, as to New Zealand, next to impossible, considering the distance it would have to travel over the ocean, and the extraordinary combination of favourable circumstances that must have arisen before it could possibly have become established in such locality.
And why should this butterfly be thought to have been introduced any
more than Pyrameis itea, Hamadryas zoilus, or Diadema bolina (auge, Cramer), the two former of which occur in Australia, and the latter in the East Indies, as well as in New Zealand? I think it far more reasonable to suppose that at some distant time New Zealand and Australia were connected with Asia by the present intermediate islands and other land now submerged, or so nearly connected that winged insects might have passed from the one locality to the other. The identity of many Australian and New Zealand species of insects with species inhabiting China and the East Indies tends to favour such supposition.
The occurrence of Danais berenice in New Zealand, after not having been seen in the colony for some years previously, would seem to be analogous to the intermittent occurrence in Britain of Vanessa antiopa, Colias edusa, Sterrha sacra, and some other species of Lepidoptera which have not yet been satisfactorily accounted for, although many entomologists think it due to some peculiar condition of climate or other circumstance necessary to the development of these insects, and that they lie dormant in the ova or pupa state until the happening of such condition or circumstance.
Whether the theory of the introduction of this butterfly into Australia and New Zealand has been supported by any argument or evidence I am not aware, but, in opposition to such theory, I would add the following remarks to the arguments I have already used:—
Firstly. As to its introduction purposely.
We have no record of such introduction, and it is not likely that anyone would take the trouble to introduce it.
It possesses no value but as an ornament, and that it would be selected from among so many far more handsome and attractive butterflies is highly improbable.
I know of no instance of successful attempts to introduce a living butterfly from one disconnected country to another, and the ova of butterflies are not readily procured, neither are the larvæ easily reared.
The appearance of the butterfly at Hawke Bay and Hokitika—places so far apart—without any record of its occurrence in intermediate localities, is inconsistent with the theory of its introduction purposely, unless we are to suppose that the introduction was repeated, or that the person introducing it took the trouble of introducing it at both places.
Secondly. As to its introduction accidentally.
The “blown-over” theory entertained by many entomologists with respect to the appearance in England of butterflies rarely seen there, but common on the continent of Europe, cannot be reasonably applied in this case. That a butterfly could be blown over such an expanse of ocean as it must travel over to reach New Zealand seems to me impossible. Even were it strong enough
on the wing to accomplish such a flight, its natural habit of resting at night would cause it to perish in the water. The boldest advocate of such a theory would scarcely venture to assert that a butterfly has been known to, or would under any circumstances, continue its flight at night; and if this butterfly were so introduced, why not other butterflies, and the large hawk-moths so infinitely stronger and swifter on the wing. The tales of clouds of butterflies seen at sea, thousands of miles from land, are as unreliable as those of the sea serpent.
It is possible, but not probable, that it may have come over in some ship; that it may have entered the cabin or settled in some part of the ship, and having remained there during the voyage, been set at liberty in New Zealand.
It is possible, but not probable, that ova, larvæ, or pupæ may have been introduced with some shrub or plant.
Thirdly. As to its introduction, either purposely or accidentally.
Supposing the butterfly, ova, larvæ, or pupæ to be so introduced, it would be necessary, for the propagation of the species, that the butterfly should be an impregnated female; that it should lay its eggs upon its accustomed foodplant, or upon some other plant that the larvæ would eat (and it is well known how difficult it is to induce the young larvæ of a butterfly to accept for food any other kind of plant than that upon which the larvæ of a like species of butterfly are accustomed to feed); that at least two of the larvæ should escape the numerous enemies and dangers to which they are subject, and attain the pupa state; that the pupæ should survive, and in due time produce a perfect male and a perfect female butterfly; that such male and female should copulate; and that the female should survive through all dangers until she deposited her eggs upon the food plant.