APPENDIX TO CHAP. II, OF BOOK III,

CONTAINING

Observations on the Sugar Ants in the Island of Grenada; extracted from a letter of John Castles, Esq. to Ge-. neral Melville: read before the Royal Society in May 1790.

TH

HE sugar ants, so called from their ruinous effects on sugar cane, are supposed to have first made their appearance in Grenada about the year 1770, on a sugar plantation at Petit Havre; a bay five or six miles from the town of St. George, the capital, conveniently situated for smuggling from Martinico: it was therefore concluded, they were brought from thence in some vessel employed in that trade, which is very probable, as colonies of them in like manner were afterwards propagated in different parts of the island by droghers, or vessels employed in carrying stores, &c. from one part of the island to another.

From thence they continued to extend themselves on all sides for several years destroying in succession every sugar plantation between St. George's and St. John's, a space of about twelve miles. At the same time, colonies of them began to be observed in different parts of the island, particularly at Duquesne on the north, and Calavini on the south side of it.

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All attempts of the planters to put a stop to the of these insects having been found ineffectual, it well became the legislature, to offer great public rewards to any person who should discover a practicable method of destroying them, so as to permit the cultivation of the sugar cane as formerly. Accordingly, an act of assembly was passed, by which such discoverer was entitled to twenty thousand pounds, to be paid from the public treasury of the island.

Many were the candidates on this occasion, but very far were any of them from having any just claim; nevertheless, considerable sums of money were granted, in consideration of trouble and expenses in making experiments, &c.

In Grenada there had always been several species of ants, differing in size, colour, &c. which however were perfectly innocent with respect to the sugar cane. The ants in question, on the contrary, were not only highly injurious to it, but to several sorts of trees, such as the lime, lemon, orange, &c.

These ants are of the middle size, of a slender make, of a dark red colour, and remarkable for the quickness of their motions; but their greatest peculiarities are, their taste when applied to the tongue, the immensity of their number, and their choice of places for their nests.

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All the other species of ants in Grenada have a bitter musky taste. These, on the contrary, are acid in the highest degree, and when a number of them were rubbed together between the palms of the hands, they emitted a strong vitriolic sulphureous smell; so much so, that when this experiment was made, a gentleman conceived that it might be owing to this quality that these insects were so unfriendly to vegetation. This criterion to distinguish them was infallible, and known to every one.

Their numbers were incredible. I have seen the roads coloured by them for miles together; and so crowded were they in many places, that the print of the horses feet would appear for a moment or two, until filled up by the surrounding multitude. This is no exaggeration. All the other species of ants, although numerous; were circumscribed and confined to a small spot, in proportion to the space occupied by the cane ants, as a mole hill to a mountain.

The common black ants of that country had their nests about the foundation of houses or old walls; others in hollow trees; and a large species in the pastures, descending by a small aperture under ground. The sugar ants, I believe, universally constructed their nests among the roots of particular plants and trees, such as the sugar-cane, lime, lemon, and orange trees, &c.

The destruction of these ants was attempted chiefly two ways; by poison and the application of fire.

For the first purpose, arsenic and corrosive sublimate mixed with animal substances, such as salt fish, herrings, crabs, and other shell fish, &c. were used, which was greedily devoured by them. Myriads of them were thus destroyed; and the more so, as it was observed by a magnifying glass, and indeed (though not so distinctly) by the naked eye, that corrosive sublimate had the effect of rendering them so outrageous that they destroyed each other'; and that effect was produced even by coming into contact with it. But it is clear, and it was found, that these poisons could not be laid in sufficient quantities over so large a tract of land as to give the hundred thousandth part of them a

faste.

The use of fire afforded a greater probability of success; for (from whatever cause) it was observed, that if wood, burnt to the state of charcoal, without flame, and immediately taken from the fire, was laid in their way, they crowded to it in such amazing numbers as soon to extinguish it, although with the destruction of thousands of them in effecting it. This part of their history appears scarcely credible; but, on making the experiment myself, I found it literally true. I laid fire, as above described, where there appeared but very few ants, and in the course of a few minutes thousands were seen crowding to it and upon it, till it was perfectly covered by their dead bodies. Holes were therefore dug at proper distances in a cane piece, and fire made in each hole. Prodigious quantities perished in this way for those fires, when extinguished, appeared in the shape of mole hills, from the numbers of their dead bodies heaped on them. Nevertheless the ants soon appeared again, as numerous as ever. This may be accounted for, not only from their amazing fecundity, but that probably, none of the breeding ants or young brood suffered from the experiment.

For the same reason, the momentary general application of fire by burning the cane trash (or straw of the cane) as it lay on the ground, proved as little effectual; for although, perhaps, multitudes of ants might have been destroyed, yet in general they would escape by retiring to their nests under cover, out of its reach, and the breeding ants, with their young progeny, must have remained unhurt.

This calamity, which resisted so long the efforts of the planters, was at length removed by another; which, however ruinous to the other islands in the West Indies, and in other respects, was to Grenada proved a very great blessing; namely, the hurricane in 1780; without which it is probable, the cultivation of the sugar-cane in the most valu

able parts of that island must have in a great measure been thrown aside, at least for some years. How this hurricane produced this effect, has been considered rather as a matter of wonder and surprize than attempted to be explained. By attending to the following observations, the difficulty, I believe, will be removed.

These ants make their nests, or cells for the reception of their eggs, only under or among the roots of such trees or plants, as are not only capable of protecting them from heavy rains, but are at the same time so firm in the ground, as to afford a secure basis to support them against any injury occasioned by the agitation of the usual winds. This dou ble qualification the sugar cane possesses in a very great degree; for a stool of canes (which is the assemblage of its numerous roots where the stems begin to shoot out) is almost impenetrable to rain, and is also from the amazing numbers and extension of the roots, firmly fixed to the ground. Thus, when every other part of the field is drenched with rain, the ground under those stools will be found quite dry, as 1, and every other planter must have, observed, when digging out the stools in a cane piece, to prepare for replanting. And when canes are lodged or laid down by the usual winds, or fall down by their own luxuriancy, the stools, commonly, remain in the ground; hence, in ordinary weather, the mests of these ants are in a state of perfect security.

The lime, lemon, orange, and some other trees, afford these insects the same advantages, from the great number and quality of their roots, which are firmly fixed to the earth, and are very large; besides which, their tops are so very thick and umbrageous, as to prevent even a very heavy rain from reaching the ground underneath.

On the contrary, these ants' nests are never found at the roots of trees or plants incapable of affording the above