Art. XXII.—On the Occurrence of Danais plexippus and Sphinx convolvuli (?) in Nelson.
[Read before the Nelson Philosophical Society, 11th November, 1890.]
On October 26th I received from a resident near Bishopdale, Nelson, a fine specimen of Danais plexippus. It was unknown to me at the time by name, although I had in my possession a damaged specimen of one taken about the year 1879. In the course of the following week I heard of some six or seven others being captured in the vicinity of the town, and since that date several more have been observed.
On referring to Mr. Enys's Catalogue of the Butterflies of New Zealand, I find there a coloured drawing and a reference to it under the name of Danais archippus. It appears to have been first recorded as a New Zealand insect by R. W. Fereday in a paper printed in vol. vi. of the Transactions, and named by him D. berenice.
In vol. xi. Mr. F. W. Sturm states he saw it in Hawke's Bay in 1840 or 1841, and again in 1861. It would thus appear to occur periodically at intervals of several years.
Mr. G. V. Hudson has two specimens taken in 1879 and two taken in 1881, but from inquiries made I can find no evidence of their having been seen in Nelson since that date until the present time. And it is scarcely probable that so large and prominent an insect could escape observation.
This occasional appearance is a subject which deserves investigation. There may be several surmises by way of explanation, all more or less reasonable, and yet not satisfactory because void of proof. It may be that their usual habitat is “far from the haunts of men” on some of the back ranges or secluded mountain-gullies, from which a succession of strong winds similar to those we have lately experienced has driven them; or, as is the case with some insects in England, the larva may require some four or five years to mature.
Whatever may be the cause, it is well from time to time to notice their presence, in order to assist in unravelling the tangled web of their life-history. There is no description, as far as I am aware, in the Transactions, but I have, through the kindness of Mr. G. V. Hudson, received the following copy of Boisduval's description:-
Danais plexippus, Linn. Danais archippus, D. berenice (in Transactions), Anosia plexippus.
The four wings somewhat sinuate, fulvous above, with a rather brilliant reflection; all the wings entirely margined with deep-black, having in fresh specimens a bluish reflection; nervures same colour. The summit of the primaries has three oblong fulvous spots, preceded by eight or ten smaller white or yellowish-white, extending to the middle of the upper edge, two rows of white spots on the outer borders of all the wings; occasionally the inner row is ferruginous. The fourth nervure of the secondaries has a large black spot or tubercle. The under side presents the same markings as the upper, but the points of the posterior edge are larger and all white. The ground-colour of the secondaries is nankin-yellow, with the nervures slightly bordered with whitish. The emarginations of all the wings white. Body black, with yellowish points on the thorax and breast.
The ♀ has wider nervures, and is destitute of the black tuberculous spot on the secondaries.
Expanse of wings, 4 ½in.
I have also to exhibit two fine specimens of a moth which Mr. Hudson identifies as Sphinx convolvuli. They were captured in Nelson during the past week. Mr. Meyrick, in vol. xxii. of the Transactions, describes it, and mentions it as being found in Taranaki and Napier, and that the larvæ feed upon the wild convolvuli of the sea-shore.
From a description of the larva, I should say it is identical with the one that I am informed has been seen for several years feeding on the convolvuli in Blind Bay district.
I also have to record the occurrence of the somewhat rare and beautiful moth, Elvia glaucata, in Nelson, but, unfortunately, my specimen was destroyed. Mr. Meyrick mentions it as found in Christchurch from December to February, but I captured it early in the month of October.