Art. LXIII.—On Cordiceps robertsii.
[Read before the Wellington Philosophical Society, 31st July, 1895.]
The term “vegetable caterpillar” is a corruption of the old name of “vegetating caterpillar,” by which the Sphœria was called forty or fifty years ago by those colonists who then took interest in scientific matters, and which properly describes the curiosity as a caterpillar which apparently developes into or produces a plant. I think it a pity that our Transactions should be disfigured by a vulgar corruption, however common.
Sphœrias are far more common than is generally supposed. As many as fifteen or twenty have occasionally been found, in my presence, in the course of a few hours, when forming a short length of side-cutting, and no doubt many others were dug up without being observed. This has always occurred in koromiko scrub or the lightest of scrubby bush—rangiora, karamu, tutu, &c. Though I have heard it asserted that Sphœrias were generally found under rata-trees, I never yet met with one in such a situation, but have often seen them dug out in places a mile or more from a rata. Although, as a rule, there is only one shoot, and that proceeding from the back of the caterpillar's neck, yet an instance is recorded, I think in our Transactions, of shoots proceeding from both ends of the insect. It often happens, too, that, if the original shoot has been broken off by any accident, a second one springs up alongside it to replace it. Again, it is by no means unusual for the shoot to fork above ground and produce two spikes of sporangia, and these sometimes fork again; so that, in one instance which one of my sons found at Momahaki, beyond Waitotara, there were eight or more spikes.
As regards the main question started in Sir W. Buller's paper,* I may note that, if a Sphœria is divided longitudinally,
[Footnote] * Trans. N.Z. Inst., vol. xxvii., art. xii.
it will be found that the alimentary canal of the insect still remains perfect, only the flesh having apparently been converted into the white cork-like vegetable substance. Outside of this there is a thin brown covering, which I have always regarded as the skin of the insect; and, as this is thicker and darker in colour at the horny portions, such as the head and feet, and these retain their exact form, even to the claws of the feet, I do not think that any one would be likely to regard them as other than remaining portions of the original insect. The total quantity of them, however, is so small that I hardly fancy that they would give any appreciable result to a chemical test, such merely as the smell of chitine when burnt.
I have usually seen Sphœrias dug out in the late autumn and early winter months. In earlier autumn they are of a green tint, and so are more liable to escape notice; and earlier still in the season I have often seen the live caterpillars dug out. They are of about the colour of parchment, and might easily be mistaken for silkworms. I believe that the Maoris are right in stating that they are the larvæ of the large green night-moth œpialus; yet, in the course of the many years during which I lived for the most part in the bush, and kept a look-out for them, I never saw the caterpillars feeding on the leaves of plants of any kind, though the aweto (larva of the sphinx-moth) may often be observed on the convolvulus, particularly on the stunted form which grows among the sandhills near the sea-coast. Some people fancy that the aweto is the vegetating caterpillar; but this is a mistake—they are quite different; and the former is unmistakable, from its larger size, varying colours (green, yellow, or reddish-brown), and particularly by having a sort of horn growing erect on the tail-end of the insect.