Art II.—Note on an Aphidian Insect infesting Pine Trees, with observations on the name “Chermes” or “Kermes.”
[Read before the Wellington Philosophical Society, 6th August, 1884.]
Some four or five years ago the imported pine trees in this country began to be attacked by a “blight,” (to use the popular term) which has since increased to a somewhat alarming extent throughout the colony, at least in Wellington, Nelson, and Canterbury. The trees most subject to this pest appear to be Pinus halepensis, P. insignis, and P. silvestris. The general appearance presented is that of a white, mealy or cottony, fluff thickly coating the twigs of the tree but not extending far along the leaf-tufts. These last, however, soon become dry and brown, as if scorched, and
generally the whole tree seems to wither, until at last it presents the appearance of complete destruction. The aspect of the pest is always unpleasant, and as its ravages increase it becomes more and more repulsive, and trees formerly vigorous, full-foliaged, and handsome, become sickly, meagre and unsightly.
My attention was first called to this “blight” a few months ago at Nelson, where it was doing immense damage to Pinus silvestris. It appears to be very common about Wellington, P. insignis and P. halepensis in the Botanical Gardens and elsewhere being greatly infested by it. I hear also that in plantations of pines near Wanganui, Christchurch, Ashburton and Peel Forest, its ravages are extending with great rapidity and effect.
The insect causing the injuries just mentioned belongs to the family “Aphididæ,” part of the order “Homoptera,” an order which has as yet been by no means sufficiently studied either in New Zealand or in other countries. It belongs undoubtedly to the germs which, by Kaltenbach, Passerini, Buckton, and others, is included under the name “Chermes” or “Kermes.” [As regards this name, see my observations below.] But I am not able to fix accurately its specific position at present, in the absence of certain information on some points. Its nearest allies appear to be Chermes (Anisophleba) pini, Koch, and C. corticalis, Kaltenbach, if indeed these two insects are not one and the same; but, as shown presently, there are a few characters which seem to distinguish it from both. Just now, therefore, I can only suggest for it a temporary scientific name.
It was remarked above that, after continued exposure to the attacks of this insect, the trees present the appearance of complete destruction. I purposely employ this somewhat vague phrase, because of the uncertainty of the thing so far. Undoubtedly, in many instances, nothing can seem more like approaching death, and often complete death, than the aspect of the infected trees. But I am informed by Mr. Buchanan, and others who have watched them for some time, that in the majority of cases the trees, after a year or two, recover and become quite green again; indeed, I understand that they have not found any tree actually killed by the insect. If this is found to be generally the case, of course the damage done will be lessened,—not that the two or three years of decay and weakness will not be harmful, but at least there will be the chance that the trees may take a fresh start afterwards. There does not appear to have been time to fully study this point in New Zealand. It may be that, like a very severe but not constitutional disease, the pest may leave no permanent injury behind it; it may be, on the other hand, that although seemingly recovering, the trees may never regain their proper vigour; or again, it may be that after an interval of relief the insect may come back as bad as ever, and the trees may simply
pass through alternate periods of illness and apparent health, and never be really what they should be. At present we only know, as it were, the first stages of the malady.
I find no particular mention anywhere of permanent deadly injury done by Chermes in England; but we cannot judge with certainty from the experience at Home what might be the effects of such a parasite in a climate like ours.
As regards the methods of destroying this pest, it is not easy to suggest any certain way, on account of the mechanical difficulty of getting at the insect on branches of pine trees, covered so closely as they are with leaf tufts. But, as the Homoptera all act in the same way, by sucking through the setæ of their rostra the juices of the plants they live on, I see no reason why remedies already found useful as against the Coccidæ should not be efficacious against such an aphidian as our present insect. A great number of experiments have been made in various countries with a view to destroy Coccidæ. Some of these, which are applicable to deciduous orchard trees, where the insect is easily approached as it lies on the bark (such, for example, as the different oil mixtures, kerosene, etc.), are not available in the present instance; and, probably, the only way to attack our aphis would be by spraying over the tree some liquid remedy. There are constantly advertised in the newspapers compounds called “Scaly blight-destroyers,” and the manufacturers of these claim for them all sorts of virtues. I believe, however, that in the majority of these the chief reliance is placed upon such substances as sulphur, carbolic acid, etc., which are of no real use. Sulphur, indeed, is an excellent remedy for such diseases as oidium in vines, which are fungoid; but it seems to have no sort of efficacy as against homopterous insects. Tobacco is, in itself, most useful; but probably the cost in this country would be too great. But of all remedies the best, according to the experience of American observers, appears to be common soap. I find from Professor Comstock that a solution of a quarter of a pound of soap to a gallon of water has been found to be of very great efficacy in destroying Coccidæ of all kinds, both on deciduous and evergreen trees, on the bark and on the leaves. This being so, probably it would be also very useful against the pine insect, and is well worth trying. Of course any common soap would do if the solution is made strong enough.
In some papers lately forwarded to the New Zealand Government by the Colonial Office in London, I find a suggestion by a French gentleman for destroying Phylloxera vastatrix (also a homopterous insect) by driving copper nails into the wood of the infested vines. The idea seems to be that the insects would imbibe some salts of copper, and so be poisoned. Whether such a course would answer with pine trees and their aphidian pest I cannot say.
In cases where the trees attacked are accessible to applications of a remedy, I should say therefore that a strong solution of common soap, applied by a syringe in dry weather, might be found to be the best. Doubtless, in large plantations of tall trees say of many acres, especially if the insect is well established, it would be difficult to apply any remedy at all.
General Description of the Insect.
Suggested name—Kermaphis pini, Koch, var. lævis.
Anisophleba pini, Koch
Plate VII., figs. 1–11
Occurs in colonies surrounded by masses of white cottony secretion, clothing the twigs of pine trees. This secretion contains great numbers of apterous oviparous females, with ova and young larvæ.
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Eggs oval, yellow or brown, length about about 1/80 inch, not pedunculated (fig. 1).
Young larva just hatched, yellow, elongated oval, flattish: body segmented, the segments diminishing to the anal extremity (fig. 2): eyes brown, conspicuous. Antenna (fig. 3) of three joints, each numerously ringed, the third joint being longer than the other two together; foot normal of Aphididæ: rostrum not longer than the body; a few short spines on the segments. The larva is somewhat active.
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Apterous oviparous female dark brown in colour, semiglobular, convex above, flat beneath, resembling somewhat the Coccid insect Rhizococcus (fig. 5). Length from ½0 to 1/30 inch, breadth and height rather less. Body segmented, but without spots on the dorsum and sides. Antenna (fig. 7) very small, of three (?) atrophied joints, the last bearing some hairs. Foot (fig. 9) normal of Aphididæ. Abdomen ending in four minute but somewhat strong spines (fig. 8). Cornicles (honey tubes), none, unless the spines just mentioned may answer to them. When the insect has been macerated in potash and the interior substance expelled, the skin is found to be covered with numerous small circular orifices arranged in groups, whence is secreted the white cotton.
I am not acquainted as yet with the male, nor with the winged state of the female. According to Buckton (British Aphides, vol. iv., p. 41), the winged forms of Chermes pini are also not exactly known.
This insect differs from C. (Anisophleba) pini in the absence of peduncles in the eggs, and from both that and C. corticalis in the absence of spots on the dorsum and sides, and in the form of the female antenna. I give for comparison (fig. 11) a copy of Buckton's figure of the antenna of C. corticalis. Probably also the spines at the extremity of the abdomen may be distinctive.
Observations on the name “Chermes” or “Kermes.”
Much confusion has grown round this name, which has been made by different writers to do duty in various distinct directions. Linnæus and Fabricius included under it Coccidæ, Aphididæ, and Psyllidæ; Passerini restricts it to the Aphididæ; Kaltenbach, Buckton, and others seem to include in it Aphididæ and Coccidæ; Geoffroy, Targioni-Tozzetti, Signoret, and others restrict it to the Coccidæ.
Now, there is so marked a distinction between the families just mentioned that it seems simply absurd to confound them under one name. A number of characters which can only be well made out under the microscope distinguish them completely; but, apart from these, the fact that in the Coccidæ the females are always, without any exception, apterous, whilst in the Aphididæ the females in certain stages have four wings, is a perfectly sufficient cause for separation. Attempts have been made at various times to introduce a clearer classification, but, amongst at least English writers, with little or no success. This appears to me to be due in a great measure to the very small knowledge possessed by English naturalists of the family Coccidæ, a family which is apparently not abundant in England except upon exotic plants. In point of fact, most of these writers seem not to be aware of anything more than the single genus “Coccus,” to which, although in reality it contains only the single species C. cacti (cochineal), they relegate every insect of the family.* It is from some such want of knowledge that the name of “Chermes” or “Kermes” has been given to many quite distinct insects, even in some cases to Psyllidæ.
I am quite well aware that names are not an end, but a means to an end, and that a rigid and precise purism may be often absurd; yet I see no reason why accuracy should not be aimed at in the case of minute insects as in the case of larger animals; and I can fancy the chorus of indignant and contemptuous expostulation which would greet an ornithologist combining under one genus a hawk and a magpie, or a geologist including a trilobite amongst the saurians.
The name “Chermes” or “Kermes” is, so to speak, as old as the hills. It appears to have been originally given by the Persians either to the insect itself which produced for them a red dye (not cochineal), or to the dye thus produced. Linnæus applied the name to an insect which he termed Kermes ilicis, and unfortunately began the confusion to which I am referring, as he
[Footnote] * Thus, for example, Mr. Beck, in the Journal of the Roy. Microsc. Society, describes at some length what he calls a “Coccus” of the apple tree, which is, of course, Mytilaspis pomorum; and Mr. Buckton (British Aphides), who mentions constantly “Coccus,” refers to an insect as “now Coccus ilicis,” which is not a Coccus at all, but a combination long ago abandoned of Kermes bauhinii and Kermes vermilio.
included under it insects of several distinct species and even families. Gustave Planchon, in distinguishing these species, defined the one producing the red dye as Kermes vermilio and denominated another K. bauhinii. Both of these are true Coccidæ, and the Coccid genus Kermes may now be said to include the following European species:—
K. ballotæ, Lichtenstein.
K. bauhinii, Planchon.
K. gibbosus, Signoret.
K. pallidus, Réaumur.
K. reniformis, Réaumur.
K. variegatus, Gmélin.
K. vermilio, Planchon.
From America a species, K. galliformis, Riley, has been described, and some others are reported, but without description, by Professor Comstock.
From South Australia I have received from F. S. Crawford, Esq., of Adelaide, a Kermes, which is undoubtedly a true Coccid, but I have not sufficient material for its full description.
All the above insects are entirely distinct from the Aphididæ in the apterous condition of the female in all stages of her existence and in almost every other character, with possibly a slight doubt as to K. variegatus.
It would seem to be only correct that, whatever might happen with regard to insects discovered or described in later times, the generic name ought to follow, and to be included in, the family of the insect which originally received the name, whether scientifically or popularly. As therefore, the above-mentioned Kermes vermilio is the undoubted representative of the old dye-producing Kermes of the Persians and Arabs, and as it is also undoubtedly a true Coccid and not Aphidian, it is right that the generic name of Kermes should be attached to the Coccid family, and that some other should be found for those Aphidians at present included under it.
Mr. Buckton (British Aphides, vol. iv., p. 22) affirms himself convinced by the arguments of Passerini, and adds, “As regard should be paid to priority, I follow Kaltenbach, Koch, and many other authors in retaining the name Chermes amongst the Aphididæ.” The same reasoning would of course lead us to extend it also to the Psyllidæ, with Fabricius, Strobelberger and Marsili two centuries ago; and this would be absurd. But, in truth, the point to be noted is that, whilst it makes no difference perhaps to which family the name is given, it is quite clear that it ought not to belong to both; and looking at the position of Kermes vermilio as stated just now, it seems most proper that this name should be restricted to the Coccidæ alone, and that some other should be found for the Aphididæ.
I venture to suggest for this purpose the name Kermaphis. It is not so far removed from the other as to be strange, and it would relieve entomology of an absurd confusion whilst still indicating something of the old relationship. On this idea, the insect above described would be Kermaphis pini var., unless the differences noted in my description should be sufficient to raise it to distinct specific rank.
Explanation of Plate VII., Figs. 1–11
1. Eggs X 20.
2. Young larva.
3. Antenna of larva X 350.
4. Rostrum of larva.
5. Oviparous female, dorsal view.
6. The same, after maceration in potash. The legs are not shown in this figure.
7. Antenna of oviparous female X 400.
8. Abdominal spines of oviparous female X 400.
9. Foot of oviparous female.
10. Pine twig infested; the leaf-tufts are cut away on the centre portion.
11. Antenna of C. corticalis, after Buckton.