DESTRUCTIVE HABITS.

It is only of late years also that the fact of their being addicted to feeding upon garden plants has been a subject of complaint.* Even up to date no special depredations occasioned by them in the Botanical Gardens, where they have been so long established, have been brought under notice, although the writer has seen there Mesembryanthemum plants partly consumed by them. W. French, whose duties as propagator there should afford special opportunity for observing any destructive propensity that the slugs might manifest, has not been heard to regard their presence there with much concern, although for some time past it has been found necessary to protect young "annuals" from their attacks. That they may, however, prove very destructive to certain plants has now been definitely established.

The first instance of their depredations was afforded by an observation made by J. C. Boyd, of the Immigration Office, who, in 1893, remarked their presence upon the leaves of cabbage grown in the grounds attached to the offices of the Department of Agriculture, and further noticed that they made large holes therein as they fed upon their tissue. This discovery has since been confirmed abundantly by others. Thus M. B. Bernays states generally they partake of "tender plants of all descriptions, be they vegetables or flowers; also, that they eat cauliflowers, cabbages, turnips, broad beans, lettuces amongst esculents; and stocks, cinerarias, dianthus, &c., amongst ornamental plants. Asparagus they eschew, even the tender shoots of fancy varieties being avoided." To this list may be added, on the authority of another observer, carrots, eschalots, tomatoes, and young dahlias. Newly planted Coleus cuttings they will again wholly consume. Indeed, so Indeed, so emphatically has this destructive habit been displayed, that a correspondent who has experienced their depredations has been led to anticipate that "if they are not stopped in their ravages they will soon-i.e., in a few years become quite as much of a curse in the vegetable garden as is the Fruit Fly (Tephritis) in the orchard." It is generally in their early stages of growth that plants subject to these attacks are injured; and this is sometimes exclusively the case. In addition to the kinds above mentioned they also reject many others, e.g., the pea, and fortunately do not attack the ordinary grasses. On the other hand they consume some of our weeds, e.g., Fat Hen (Chenopodium). Hence the lessening degree to which this plant is to be remarked as present in our local waste places.

J. C. Boyd, who, as already remarked, was the first in Queensland to bring under notice the destructive propensities of Vaginula Slugs, states that they are very partial to the ripe fruit of the tomato, climbing up the plants themselves to gain access to it; that they will even gnaw through the hard rind of the under surface of pumpkins, when these are lying on the ground, and thus determine the invasion of a special form of rot that originates at the site of injury; that they are especially addicted to attacking cabbages, cutting down the young plants, and eating holes (vide Plate) in the under leaves of older ones; that they are very destructive to French beans; that other vegetable garden plants, also, they may partake of, especially when these are quite young. Parsley heads they do not seem to affect, though they will eat mint. Strawberry plants, again, remain comparatively untouched, only the tips of the young shoots being at times injured.

DESCRIPTION.

The following general description, supplemented by a study of the accompanying plate, whereon are depicted life-size photographic representations of the slugs themselves, will aid in their recognition :

They are elongate-oblong in outline, their length and breadth being as 3 to 5 when non-extended and at rest, whereas they are four times as long as broad, or even relatively longer, when stretched out as they are when crawling. They are

*Although the species of Vaginula are of such numerous occurrence within the tropics, the writer can only recall a single instance of destructive habits being attributed to them. Thus Dr. P. Fischer writes :-"Ils ravagent les plantations de café, de tabac, ainsi que les jardins potagers.' --Manuel de Conchylioloque, p. 493 (1887).

narrowed both forwards and backwards, the front and hind extremities being rounded and projecting both over the head as well as the tail end. The upper surface has a uniform contour, and is gently convex from side to side, and slopes downwards also to both the fore and hind end. It is also of a dull aspect, though moist, no mucous being poured out as in ordinary slugs. It is, moreover, completely occupied by fine granules and intervening pores. It is known as the mantle. In front are two pairs of tentacles arising from the head. The upper pair are stout, finely ringed, and end in a knob containing a minute eye spot. Beneath these are two, even stouter ones; these are much shorter than the preceding, and are terminally cleft, or each ends in two distinct tubercles. The under surface, which is lighter coloured than the upper, is almost quite flat, and is divided into three distinct portions, each extending the length of the slug. The central of these is the so-called foot, and that on each side is the under portion of the mantle. These three divisions may be equal in width, or the foot may be less than a third of the breadth. This foot has a more glossy lustre than has the remaining portion of the flat under surface, owing to the presence of mucous. It is also crossed by closely placed very fine lines or striæ. The head may be withdrawn to a greater or less extent into a cavity. The mouth organs include the ordinary jaw and radula. The arched and longitudinally folded, whilst the latter carries longitudinal series of cusp-bearing teeth. The male genital orifice is just behind the right lower tentacle, whereas the female one is at the side beneath, near the right border of the foot, not far from the middle of its length. The animal has the two sexes combined in one individual. The adults in both species measure 3 inches in length as ordinarily extended during crawling.* They may be distinguished one from the other by the following characters :

Vaginula Leydigi, Simroth, when fully developed, is pitchy-brown or almost black above, and there extends along the centre of the back a fine yellowish line, which does not quite reach either end. The back also is gently and regularly curved from one side to the other. The under surface is of a brownish-white colour, the foot having a slight yellowish hue. The latter, extending from one end to the other, occupies about a third of the breadth.

When young the animal is of a much lighter colour, it being usually palebrown, with numerous dark-brown specks above, these often forming an obscure network. Beneath it is greyish-white.

The eggs are soft, translucent, oval, slightly flattened at one extremity, about twice as long as broad, and of a honey-yellow colour. These appearances being partly due to the nature and form of their contents: for they are surrounded by a thick transparent colourless covering that presents at one extremity a short thick blunt prolongation. They are large, measuring 8 mm. (4 lines) x 4 mm. (2 lines).

Vaginula Hedleyi, Simroth.-This species is of a pale yellowish-brown or drab colour above. The upper surface also is not as convex as is the back of V. Leydigi, and not so uniformly arched from side to side, being somewhat flattened towards each lateral border. Beneath it is brownish-white. The central area or foot does not occupy a third of the breadth, but only two-thirds or less thereof. The eggs are generally similar in appearance to those of the preceding species, but are distinctly smaller, measuring 65 mm. (3 lines) x 35 mm. (14 lines).

A close insight into the anatomy of these two species, as Dr. Simroth has remarked, reveals a surprising amount of difference also in the form of almost all their internal organs. For an indication of the nature of this-which is beyond the scope of this article to describe-reference must be made to either of the two memoirs that have emanated from him, and that have been already alluded to (page 64). It must be understood, however, that it is in these structural details that the characteristic features of the two species reside.

Generally speaking, they may be stated to resemble the slug-like mollusc of such frequent occurrence under logs and stones in mangrove swamps, and which are referable to the genus Onchidium-so much so indeed that earlier writers, e.g., Guilding, confounded the two under this one title.

HABITS.

The Vaginula slugs are almost exclusively nocturnal in their habits, though they may be found early during wet mornings on the move, usually, however, engaged then in returning to their haunts. They creep readily over the ground and even along perpendicular walls, and travel relatively long distances without intermission. These haunts are-beneath logs, old timber, stones, and rubbish generally; underneath the floors of out-houses; in bush-houses or shade-gardens; in dry walls; and wherever in fact dark damp hiding-places near the ground can be found. They also enter cracks and other openings into the soil, and even burrow into this when it is loose, being able by extending their bodies to squeeze through quite narrow passages. Thus they will insinuate themselves amongst the roots of plants, especially when these form a more or less compact mass. In the latitude of Brisbane they almost entirely hibernate; and are thus to be found during May, June, and July both night and day, not only in any of the above hiding-places but also often beneath stones some inches from the surface. Here they usually occur, congregated together, both young and old. When removed, however, although at first they are motionless and contorted, they are not long in displaying evidence of vitality and thus proceed to "make off." When crawling over rough surfaces they are wont to discharge from the surface of the foot a thin layer of transparent mucous, which soon dries and becomes a transparent shining film. This, however, they do not do to the same extent as do ordinary slugs (Limax, Arion, &c.)

They are oviparous, and deposit their batch of eggs beneath stones or logs, usually in shallow cavities. Each slug lays forty* or more eggs, and these are both large and conspicuous, as described. They issue from the side of the body, beneath, as represented natural size on Plate CXIX. The eggs have a moist sticky surface that causes them to adhere, to a certain extent, to foreign bodies. They are placed as laid in a single mass-the individual eggs being held together not only by their natural adhesiveness, but also by threads of a clear mucous-like matter. The entire lump may also be covered by fragments of slug-excrement that may serve to mask their true nature. The process of egglaying seems to occur at intervals throughout the summer months, being continued until almost the end of April; and as each slug is both a father and a mother-though congress of two may be required that reproduction ensuea few individuals soon give rise to a very numerous progeny, and hence the hordes in which they occur. The time occupied in arriving at maturity has not been ascertained. So also the duration of their natural lives.

NATIVE COUNTRY.

There are good grounds for considering that though these particular species of Vaginula Slugs have not been described as occurring in any other country, or have not been identified with any of the species noted as existing elsewhere, they are to be regarded as importations. The grounds on which this conclusion. is based are the following:

(1.) For a considerable time after they had been first noticed in Brisbane, no evidence of their occurring in the district beyond the small area in which they were then to be met with was forthcoming, notwithstanding close scrutiny into the nature of our local molluscan fauna on the part of others as well as especially on that of the writer had been made: nor have explorations by naturalists in different parts of Queensland revealed their presence further afield amongst other related denizens of the scrub and bush.

(2.) They are quite of a different type from the other members of the failym Vaginulide that have been reported as occurring in Queensland, and which are prismatic, instead of being plano-convex in section, and which hence-as well as on other grounds-have been relegated to the genus Atopos by Simroth (Zeitsch. f. Wiss. Zool., vol. lii. 1891). This objection is not, however, wholly tenable, since Vaginula and Atopos co-exist in the Philippine Islands.

An individual of the light-coloured species, V. Hedleyi, laid whilst under observation fiftyfive eggs, and twenty-two eggs were found in apposition to an example of V. Leydigi.

(3.) The species of Vaginula, although very numerous, only exceptionally extend so far from the equatorial region as is the latitude of Brisbane--27 degrees south-where they have to hibernate.*

(4.) For some considerable period prior to their discovery, the Brisbane Botanical Gardens had received, from time to time, consignments of plants from regions in which either Vaginula Slugs are already known to occur, or may be expected with great probability to be found. And the fact that they remained undescribed until 1889, and have not as yet been identified with species indigenous to other lands, is intelligible when it is recognised that the Vaginulide of certain climes, apparently rich in species-e.g., in the East Indies have exceptionally been made the objects of systematic study. They were, however, undoubtedly undescribed (selbstverständlich neu, to use the words of Dr. Simroth in his first-mentioned memoir) when C. Hedley first made them the object of special study, though at the time of writing this paper (September, 1889) it does not appear to have occurred to him that they were not truly indigenous to Southern Queensland. It is satisfactory, however, to be able to state that the opinion of the writer with regard to this question is now shared by so competent an authority; for C. Hedley, in a recent communication, states as follows:

I always did suspect these slugs to be foreign, and your information that they have increased so as to count amongst "Pests" confirms the idea. That the many active collectors who have searched Queensland for Mollusca, including ourselves. have never met with it elsewhere is a suspicious circumstance. That it should occur in the Botanical Gardens suggests introduction with foreign plants. It is remarkable that any species should first be made known to science in the person of erratic wanderers from native soil. You will recall the case of Bipalium kewense as a parallel one. I cannot at the present moment remember another. On the other hand, this is a genus that might be expected to occur in Queensland. Two of its alliesAtopos australis, Heynemann, and A. prismatica, Taparone-Caneffri-are already reported from your territory. From New Caledonia a still nearer relation is found in Vaginula plebeia, Fischer.-Australian Museum, in lit., 15-5-99.

NATURAL ENEMIES.

None of our

This aspect of the subject has not as yet claimed attention. native birds have been observed engaged in feeding upon these slugs, though it is anticipated that the latter might be favoured by the Ibis. The same remark applies to our indigenous batrachians-frogs and toads; but their numbers and rate of increase seem to far exceed the capabilities of this description of possible slug-enemies. No Acari have been found preying upon the beetle larvæ, as is sometimes the case with ordinary slugs elsewhere. But on two occasions M. B. Bernays "has noticed a steel-blue red-headed centipede ? Heterosoma sp.), about 4 in. in length, on the backs of large individuals of the blackish-coloured variety of Vaginula, which latter were practically in their embraces. The slug in each case at the time moved vigorously, but its captor seemed to have full charge. In fact, it seemed to be a struggle for existence on the part of the former." This predatory habit, however, is one which, for obvious reasons, could not be availed of in practical procedures having for their object the repression of the pest. Domestic poultry-including ducks, which are under certain circumstances ravenous true slug-consumers-do not appear to affect Vaginulas, or, if they partake of them, have not appreciable influence in lessening their numbers.

PREVENTIVE MEASURES.

As this slug has so well established itself in the district, and has manifested not only its adaptability to our climate, but also its powers of rapid increase in numbers, as well as its capability of injuring garden plants, its further dissemination

The Vaginula Slugs are essentially tropical or subtropical animals, occupying a zone extending about 20 degrees on each side of the equator, being known to occur, almost invariably within this torid region, in South America, Mexico, West Indies, East Central Africa, Mauritius, the Seychelles, Ceylon, Burmah, South China, and the East Indies. Exceptionally they pass beyond this limit, being found (according to Dr. Semper) on both sides of South America to 38 degrees of south latitude along the coastal districts, and they have also been reported from Hongkong (23 degrees north latitude).

should, if possible, be opposed. Although its capability for extending its range of occurrence-as a result of the exercise of its natural faculty of locomotionis relatively great, there are grounds for concluding that its present distribution has been principally brought about, unintentionally, through traffic in living plants The slug has been found even within flower-pots containing growing ferns, having doubtless entered at the drainage-hole when in an immature condition; it has also been met with in cases in which plants have been either established or packed, prior to transmission; and, moreover, its eggs have been remarked in the soil which these boxes have contained. In fact, any case of plants left during a summer's night in a spot frequented by them, unless a specially tight one, is almost certain to be visited by, and subsequently harbour, the pest. The roots of certain plants, and, above all, densely-clothed rhizomes, even when all soil has been removed, may again be occupied by the slug or its eggs. Bird's-nest ferns, if left lying upon the ground in the haunts of the animal, offer a favourite retreat for it. It is accordingly expedient that all plants, and the packages that have contained them, be carefully examined upon their receipt, and the soil, if practicable, burned. The roots, again, should be washed under a tap to remove any adherent matter, care being especially taken that no slug, however small, or slug's egg, be allowed to escape detection and destruction. Consignors of plants should also be required to forward themwhenever practicable-without any soil being contained in the case or package. These injunctions, moreover, are applicable to plants that are received from all tropical or sub-tropical lands, as well as to those transmitted or brought from Brisbane or its suburbs. They should be especially respected by those residing along our sea-board. The climatic conditions obtaining west of the Dividing Range may, it is thought, prove an obstacle to their establishment in that part of the colony-except quite locally there, in shade-gardens or bush-houses.

When slugs are established in the immediate neighbourhood of a garden, or have even already become denizens of the cultivation itself, it is still possible to protect portions of land that are either already free from or have become artificially relieved of their presence, by the employment of certain deterrents. Amongst these the use of "tobacco-waste" may especially be recommended. This is composed of the discarded mid-rib, or stout central rib, of the leaf after it has been cured, and at present may be obtained at tobacco factories at a merely nominal cost, say about 5s. per load. Applied to land, it has also the additional value arising from the fact that it is a fertiliser. Indeed, it is already availed of by pineapple-growers on account of possessing this feature. This waste has simply to be laid upon the soil so as to form a barrier around the portion of ground that it is purposed to protect from the slugs' visitations. A band of the width formed by three or four pieces of tobaccowaste laid side by side has been found, in the course of an experiment, to be adequate to confine the slug in a space of but a foot or two square, from which it would effect its escape in a few minutes were no such obstacle present to intercept its progress. On contact with this material, it secretes a thin film o transparent mucus from its strap-like foot, as if to protect it from injury. Should it succeed in finding its way on to a few pieces of the tobacco, its progress is soon stayed, and death ensues; for this material is not only repugnant but is also fatal to the pest. Already the employment of tobacco-waste, as has been stated by more than one correspondent, has been successfully resorted to in dealing with anticipated incursions of this slug. Of course, also, the application of tobacco-extracts-more than one of which is on the market-might be expected to prove similarly effective; but in using them it would be necessary to impregnate some absorbent powder with the fluid. Their employment, however, would involve a greater cost than would be involved in that of the waste product mentioned.*

In mentioning the use of tobacco-waste, it is due to the writer to acknowledge his obligations to Mr. A. J. Boyd, editor of the Queensland Agricultural Journal, who was the first to bring under his notice an instance of its successful employment for the purpose mentioned.