Sketches of the Natural History of Ceylon Part 48

DIPTERA. _Mosquitoes_.--But of all the insect pests that beset an unseasoned European the most provoking by far is the truculent mosquito.[1] Next to the torture which it inflicts, its most annoying peculiarities are the booming hum of its approach, its cunning, its audacity, and the perseverance with which it renews its attacks however frequently repulsed. These characteristics are so remarkable as fully to justify the conjecture that the mosquito, and not the ordinary fly, const.i.tuted the plague inflicted upon Pharaoh and the Egyptians.[2]

[Footnote 1: _Culex laniger?_ Wied. In Kandy Mr. Thwaites finds _C.

fuscanns, C. circ.u.mcolans,_ &c., and one with a most formidable hooked proboscis, to which he has a.s.signed the appropriate name _C. Regius_.]

[Footnote 2: The precise species of insect by means of which the Almighty signalised the plague of flies, remains uncertain, as the Hebrew term _arob_ or _oror_ which has been rendered in one place.

"Divers sorts of flies," Ps. cv. 31; and in another, "swarms of flies,"

Exod. viii. 21, &c., means merely "an a.s.semblage." a "mixture" or a "swarm," and the expletive. "_of flies_" is an interpolation of the translators. This, however, serves to show that the fly implied was one easily recognisable by its habit of _swarming_; and the further fact that it _bites_, or rather stings, is elicited from the expression of the Psalmist, Ps. lxxviii. 45, that the insects by which the Egyptians were tormented "devoured them," so that here are two peculiarities inapplicable to the domestic fly, but strongly characteristic of gnats and mosquitoes.

Bruce thought that the fly of the fourth plague was the "zimb" of Abyssinia which he so graphically describes: and WESTWOOD, in an ingenious pa.s.sage in his _Entomologist's Text-book._ p. 17, combats the strange idea of one of the bishops, that it was a c.o.c.kroach! and argues in favour of the mosquito. This view he sustains by a reference to the habits of the creature, the swarms in which it invades a locality, and the audacity with which it enters the houses; and he accounts for the exemption of "the land of Goshen in which the Israelites dwelt," by the fact of its being sandy pasture above the level of the river; whilst the mosquitoes were produced freely in the rest of Egypt, the soil of which was submerged by the rising of the Nile.

In all the pa.s.sages in the Old Testament in which flies are alluded to, otherwise than in connection with the Egyptian infliction, the word used in the Hebrew is _zevor_, which the Septuagint renders by the ordinary generic term for flies in general, [Greek: muia], "_musca_" (Eccles. x.

1, Isaiah vii. 10); but in every instance in which mention is made of the miracle of Moses, the Septuagint says that the fly produced was the [Greek: kunomyia], the "dog-fly." What insect was meant by this name it is not now easy to determine, but aeLIAN intimates that the dogfly both inflicts a wound and emits a booming sound, in both of which particulars it accords with the mosquito (lib. iv, 51); and PHILO-JUDaeUS, in his _Vita Mosis_, lib. i. ch. xxiii., descanting on the plague of flies, and using the term of the Septuagint, [Greek: kunomyia], describes it as combining the characteristic of "the most impudent of all animals, the fly and the dog, exhibiting the courage and the cunning of both, and fastening on its victim with the noise and rapidity of an arrow"--[Greek: meta roizou kathaper belos]. This seems to identify the dog-fly of the Septuagint with the description of the Psalmist, Ps.

lxxviii. 45, and to vindicate the conjecture that the tormenting mosquito, and not the house-fly, was commissioned by the Lord to humble the obstinacy of the Egyptian tyrant.]

Even in the midst of endurance from their onslaughts one cannot but be amused by the ingenuity of their movements; as if aware of the risk incident to an open a.s.sault, a favourite mode of attack is, when concealed by a table, to a.s.sail the ankles through the meshes of the stocking, or the knees which are ineffectually protected by a fold of Russian duck. When you are reading, a mosquito will rarely settle on that portion of your hand which is within range of your eyes, but cunningly stealing by the underside of the book fastens on the wrist or little finger, and noiselessly inserts his proboscis there. I have tested the cla.s.sical expedient recorded by Herodotus, who states that the fishermen inhabiting the fens of Egypt, cover their beds with their nets, knowing that the mosquitoes, although they bite through linen robes, will not venture through a net.[1] But, notwithstanding the opinion of Spence[2], that nets with meshes an inch square will effectually exclude them, I have been satisfied by painful experience that (if the theory be not altogether fallacious) at least the modern mosquitoes of Ceylon are uninfluenced by the same considerations which restrained those of the Nile under the successors of Cambyses.

[Footnote 1: HERODOTUS, _Euterpe._ xcv.]

[Footnote 2: KIRBY and SPENCE'S _Entomology_, letter iv.]

_The Coffee-Bug_.--Allusion has been made in a previous pa.s.sage to the coccus known in Ceylon as the "Coffee-Bug" (_Lecanium Caffeae_, Wlk.), which of late years has made such destructive ravages in the plantations in the Mountain Zone.[1] The first thing that attracts attention on looking at a coffee tree infested by it, is the number of brownish wart-like bodies that stud the young shoots and occasionally the margins on the underside of the leaves.[2] Each of these warts or scales is a transformed female, containing a large number of eggs which are hatched within it.

[Footnote 1: The following notice of the "coffee-bug," and of the singularly destructive effects produced by it on the plants, has been prepared chiefly from a memoir presented to the Ceylon Government by the late Dr. Gardner, in which he traces the history of the insect from its first appearance in the coffee districts, until it had established itself more or less permanently in all the estates in full cultivation throughout the island.]

[Footnote 2: See the annexed drawing, Fig. 1.]

When the young ones come out from their nest, they run about over the plant like diminutive wood-lice, and at this period there is no apparent distinction between male and female. Shortly after being hatched the males seek the underside of the leaves, while the females prefer the young shoots as a place of abode. If the under surface of a leaf be examined, it will be found to be studded, particularly on its basil half, with minute yellowish-white specks of an oblong form.[1] These are the larvae of the males undergoing transformation into pupae, beneath their own skins; some of these specks are always in a more advanced state than the others, the full-grown ones being whitish and scarcely a line long. Some of this size are translucent, the insect having escaped; the darker ones still retain it within, of an oblong form, with the rudiment of a wing on each side attached to the lower part of the thorax and closely applied to the sides; the legs are six in number, the four hind ones being directed backwards, the anterior forwards (a peculiarity not common in other insects); the two antennae are also inclined backwards, and from the tail protrude three short bristles, the middle one thinner and longer than the rest.

[Footnote 1: Figs. 2, and 3 and 5 in the engraving, where these and all the other figures are considerably enlarged.]

When the transformation is complete, the mature insect makes its way from beneath the pellucid case[1], all its organs having then attained their full size: the head is sub-globular, with two rather prominent black eyes, and two antennae, each with eleven joints, hairy throughout, and a tuft of rather longer hairs at the apices; the legs are also covered with hairs, the wings are horizontal, of an obovate oblong shape, membranous, and extending a little farther than the bristles of the tail. They have only two nerves, neither of which reaches so far as the tips; one of them runs close to the costal margin, and is much thicker than the other, which branches off from its base and skirts along the inner margin; behind the wings is attached a pair of minute halteres of peculiar form. The possession of wings would appear to be the cause why the full-grown male is more rarely seen on the coffee bushes than the female.

[Footnote 1: Fig. 4. Mr. WESTWOOD, who observed the operation in one species, states that they escape backwards, the wings being extended flatly over the head.]

The female, like the male, attaches herself to the surface of the plant, the place selected being usually the young shoots; but she is also to be met with on the margins of the undersides of the leaves (on the upper surface neither the male nor female ever attach themselves); but, unlike the male, which derives no nourishment from the juices of the tree (the mouth being obsolete in the perfect state), she punctures the cuticle with a proboscis (a very short three-jointed _promuscis_), springing as it were from the breast, but capable of being greatly porrected, and inserted in the cuticle of the plant, and through this she abstracts her nutriment. In the early pupa state the female is easily distinguishable from the male, by being more elliptical and much more convex. As she increases in size her skin distends and she becomes smooth and dry; the rings of the body become effaced; and losing entirely the form of an insect, she presents, for some time, a yellowish pustular shape, but ultimately a.s.sumes a roundish conical form, of a dark brown colour.[1]

[Footnote 1: Figs. 6 and 7. There are many other species of the Coccus tribe in Ceylon, some (Pseudococcus?) never appearing as a scale, the female wrapping herself up in a white cottony exudation; many species nearly allied to the true Coccus infest common plants about gardens, such as the Nerium Oleander, Plumeria Ac.u.minata, and others with milky juices; another subgenus (Ceroplastes?), the female of which produces a protecting waxy material, infests the Gendura.s.sa Vulgaris, the Furrcaea Gigantea, the Jak Tree, Mango, and other common trees.]

Until she has nearly reached her full size, she still possesses the power of locomotion, and her six legs are easily distinguishable in the under surface of her corpulent body; but at no period of her existence has she wings. It is about the time of her obtaining full size that impregnation takes place[1]; after which the scale becomes somewhat more conical, a.s.sumes a darker colour, and at length is permanently fixed to the surface of the plant, by means of a cottony substance interposed between it and the vegetable cuticle to which it adheres. The scale, when full grown, exactly resembles in miniature the hat of a Cornish miner[2], there being a narrow rim at the base, which gives increased surface of attachment. It is about 1/8 inch in diameter, by about 1/12 deep, and it appears perfectly smooth to the naked eye; but it is in reality studded over with a mult.i.tude of very minute warts, giving it a dotted appearance. Except the margin, which is ciliated, it is entirely dest.i.tute of hairs. The number of eggs contained in one of the scales is enormous, amounting in a single one to 691. The eggs are of an oblong shape, of a pale flesh colour, and perfectly smooth.[3] In some of the scales, the eggs when laid on the field of the microscope resemble those ma.s.ses of life sometimes seen in decayed cheese.[4] A few small yellowish maggots are sometimes found with them, and these are the larvae[5] of insects, the eggs of which have been deposited in the female while the scale was soft. They escape when mature by cutting a small round hole in the dorsum of the scale.

[Footnote 1: REAUMUR has described the singular manner in which this occurs. _Mem._ tom. iv.]

[Footnote 2: Fig. 8.]

[Footnote 3: Fig. 9.]

[Footnote 4: Figs. 10, 11.]

[Footnote 5: Of the parasitic Chalcididiae, many genera of which are well known to deposit their eggs in the soft Coccus, viz.: Encystus, Coccophagus, Pteromalus, Mesosela, Agonioneurus; besides Aphidius, a minutely sized genus of Ichneumonidae. Most, if not all, of these genera are Singhalese.]

[Ill.u.s.tration: THE COFFEE BUG. Lecanium Coffeae.]

It is not till after this pest has been on an estate for two or three years that it shows itself to an alarming extent. During the first year a few only of the ripe scales are seen scattered over the bushes, generally on the younger shoots; but that year's crop does not suffer much, and the appearance of the tree is little altered.

The second year, however, brings a change for the worse; if the young shoots and the underside of the leaves he now examined, the scales will be found to have become much more numerous, and with them appear a mult.i.tude of white specks, which are the young scales in a more or less forward state. The cl.u.s.ters of berries now a.s.sume a black sooty look, and a great number of them fall off before coming to maturity; the general health of the tree also begins to fail, and it acquires a blighted appearance. A loss of crop is this year sustained, but to no great extent.

The third year brings about a more serious change, the whole plant acquires a black hue, appearing as if soot had been thrown over it in great quant.i.ties; this is caused by the growth of a parasitic fungus[1]

over the shoots and the upper surface of the leaves, forming a fibrous coating, somewhat resembling velvet or felt. This never makes its appearance till the insect has been a considerable time on the bush, and probably owes its existence there to an unhealthy condition of the juices of the leaf, consequent on the irritation produced by the coccus, since it never visits the upper surface of the leaf until the latter has fully established itself on the lower. At this period the young shoots have an exceedingly disgusting look from the dense ma.s.s of yellow pustular bodies forming on them, the leaves get shrivelled, and the infected trees become conspicuous in the row. The black ants are a.s.siduous in their visits to them. Two-thirds of the crop is lost, and on many trees not a single berry forms.

[Footnote 1: _Racodium?_ Species of this genus are not confined to the coffee plant alone in Ceylon, but follow the "bugs" in their attacks on other bushes. It appears like a dense interlaced mesh of fibres, each made up of a single series of minute oblong vesicles applied end to end.]

This _Lecanium_, or a very closely allied species, has been observed in the Botanic Garden at Peradenia, on the _Citrus acida, Psidium pomiferum, Myrtus Zeylanica, Rosa Indica, Careya arborea, Vitex Negundo_, and other plants. The coffee coccus has generally been first observed in moist, hollow places sheltered from the wind; and thence it has spread itself even over the driest and most exposed parts of the island. On some estates, after attaining a maximum, it has generally declined, but has shown a liability to reappear, especially in low sheltered situations, and it is believed to prevail most extensively in wet seasons. While in its earlier stages, it is easily transmitted from one estate to another, on the clothes of human beings, and in various other ways, which will readily suggest themselves. Dr. Gardner, after a careful consideration and minute examination of estates, arrived at the conclusion, that all remedies suggested up to that time had utterly failed, and that none at once cheap and effectual was likely to be discovered. He seems also to have been of opinion that the insect was not under human control; and that even if it should disappear, it would only be when it should have worn itself out as other blighte have been known to do in some mysterious way. Whether this may prove to be the case or not, is still very uncertain, but every thing observed by Dr.

Gardner tends to indicate the permanency of the pest.

_List of Ceylon Insects._

For the following list of the insects of the island, and the remarks prefixed to it, I am indebted to Mr. F. Walker, by whom it has been prepared after a careful inspection of the collections made by Dr.

Templeton, Mr. E.L. Layard, and others: as well as of those in the British Museum and in the Museum of the East India Company.[1]

[Footnote 1: The entire of the new species contained in this list have been described in a series of papers by Mr. WALKER in successive numbers of the _Annals of Natural History_ (1858-61): those, from Dr.

TEMPLETON'S collection of which descriptions have been taken, have been at his desire transferred to the British Museum for future reference and comparison.]

"A short notice of the aspect of the island will afford the best means of accounting, in some degree, for its entomological Fauna: first, as it is an island, and has a mountainous central region, the tropical character of its productions, as in most other cases, rather diminishes, and somewhat approaches that of higher lat.i.tudes.

"The coast-region of Ceylon, and fully one-third of its northern part, have a much drier atmosphere than that of the rest of its surface; and their climate and vegetation are nearly similar to those of the Carnatic, with which this island may have been connected at no very remote period.[1] But if, on the contrary, the land in Ceylon is gradually rising, the difference of its Fauna from that of Central Hindustan is less remarkable. The peninsula of the Dekkan might then be conjectured to have been nearly or wholly separated from the central part of Hindustan, and confined to the range of mountains along the eastern coast; the insect-fauna of which is as yet almost unknown, but will probably be found to have more resemblance to that of Ceylon than to the insects of northern and western India--just as the insect-fauna of Malaya appears more to resemble the similar productions of Australasia than those of the more northern continent.

[Footnote 1: On the subject of this conjecture see _ante_, p. 60.]

"Mr. Layard's collection was partly formed in the dry northern province of Ceylon; and among them more Hindustan insects are to be observed than among those collected by Dr. Templeton, and found wholly in the district between Colombo and Kandy. According to this view the faunas of the Nilgherry Mountains, of Central Ceylon, of the peninsula of Malacca, and of Australasia would be found to form one group;--while those of Northern Ceylon, of the western Dekkan, and of the level parts of Central Hindustan would form another of more recent origin. The insect-fauna of the Carnatic is also probably similar to that of the lowlands of Ceylon; but it is still unexplored. The regions of Hindustan in which species have been chiefly collected, such as Bengal, Silbet, and the Punjaub, are at the distance of from 1300 to 1600 miles from Ceylon, and therefore the insects of the latter are fully as different from those of the above regions as they are from those of Australasia, to which Ceylon is as near in point of distance, and agrees more with regard to lat.i.tude.

"Dr. Hagen has remarked that he believes the fauna of the mountains of Ceylon to be quite different from that of the plains and of the sh.o.r.es.

The south and west districts have a very moist climate, and as their vegetation is like that of Malabar, their insect-fauna will probably also resemble that of the latter region.

"The insects mentioned in the following list are thus distributed:--

"Order COLEOPTERA.

"The recorded species of _Cicindelidae_ inhabit the plains or the coast country of Ceylon, and several of them are also found in Hindustan.

"Many of the species of _Carabidae_ and of _Staphylinidae_, especially those collected by Mr. Thwaites, near Kandy, and by M. Nietner at Colombo, have much resemblance to the insects of these two families in North Europe; in the _Scydmaenid, Ptiliadae, Phalacridae, Nitidulidae, Colydiadae_, and _Lathridiadae_ the northern form is still more striking, and strongly contrasts with the tropical forms of the gigantic _Copridae, Buprestidae, and Cerambycidae_, and with the _Elateridae, Lampyridae, Tenebrionidae, Helopidae, Meloidae, Curculionidae, Prionidae, Cerambycidae, Lamiidae_, and _Endomychidae_.

"The _Copridae, Dynastidae, Melolonthidae, Cetoniadae_, and _Pa.s.salidae_ are well represented on the plains and on the coast, and the species are mostly of a tropical character.