The Argentine ant

Abstract

In this bulletin the life-history of the Argentine Ant is given at length. It does not appear to have been regarded as a pest in its native country, but the authors cite references which show that it is a serious pest in certain parts of Brazil; its presence in Lisbon and Oporto was recorded in 1907 by N. Martins; Lounsbury recorded it at Capetown in 1908 and Reed at Concepcion, Chile, in July 1910. Details are given of its invasion of New Orleans and the neighbourhood more than 20 years ago, and there seems to be every reason for supposing that it was introduced into the city by means of the coffee ships from Brazilian ports. The senior author noticed colonies of this ant in the woodwork of the steamer which carried him from New Orleans to New York in July 1911 and another species, Prenolepis longicornis, was found in great numbers on board a fruit steamer from Guatemala in January 1912. The distribution of the ant in California is discussed in detail, with a map, and also its general distribution in the United States, 14 of which are more or less infested, the largest unbroken area being around New Orleans, with one or two isolated counties in the neighbouring states. The authors say that the distribution has a clear connection with the railroads, and that the only places remote from railroads where the pest has been discovered are on the banks of the Mississippi River below infested localities; they account for this by supposing that the ants have been carried on driftwood which has stranded and so established new foci. The distribution apparently is not affected by extreme variations in annual rainfall nor of mean surface temperature. The Argentine ants at the present time have attracted most attention as a household pest, invading houses in wet weather and requiring the most strenuous efforts to keep them from food of all kinds. They chiefly attack sweet articles, but also meat of all kinds and, occasionally, corn meal and wheat flour. In badly infested localities it is often necessary to place the bed-posts on sheets of glass coated with vaseline or some other repellant in order that the occupant may sleep in peace. They are very serious pests in shops dealing in food stuffs of all kinds, and also in nurseries and on ornamental plants, as by protecting the scale-insects arid plant lice they cause very serions damage. They also seriously attack orange flowers in the groves, and in market gardens they have a habit of removing certain seeds before they have sprouted, lettuce seed being particularly subject to attack. In the sugar-cane fields, in their search for the excretions of Pseudococcus calceolarias, the ants are a great nuisance. They build coverings and shelters for the scales to protect them from storms and enemies and attend to them constantly, with the result that the Mealy Bug thrives to an extent which is impossible where the ants are not present. Luckily the area infested by the Mealy Bug is at present restricted, but this insect threatens to become a more serious pest in the future, owing to the manner in which it destroys the eyes of "seed cane" and thus prevents sprouting. The control of the Mealy Bug therefore resolves itself largely into the question of how to control the ant. In corn fields the aphides are far more numerous and much more generally distributed where the ant is present. The latter also attends plant lice upon cotton, and it has been noticed in certain fields of cotton that the lice, were abundant throughout the entire summer and autumn, whereas during these portions of the year they are normally almost absent. The damage done by these ants in the orange groves of southern Louisiana is particularly serious. Fig crops are also greatly damaged, the ripening figs being bored and the interior eaten. Bee-keeping on any considerable scale is invariably abandoned when once the ants become numerous, so greatly do they interfere with the bees. In poultry yards they attack the nests of sitting hens and a broken egg will attract such numbers that the fowls abandon their nests, while young c icks are frequently killed by the incessant worry. Pyrethrum powder is found to be practically useless. The only substance which the authors say will protect sitting hens is "zenoleum" powder. Indirect injury is due to the antagonism between the Argentine ant and certain native species; thus the Fire ant. Solenopsis geminata, which is useful, in that it destroys a considerable number of Boll Weevils, is exterminated and its place taken by the far more troublesome Argentine ant. Father Biever states that they have in many cases completely exterminated the bed-bugs in the hovels and tenements occupied by poor people in the city of New Orleans. The authors then proceed to describe the insect at length, full details being given as to the methods of study adopted and a lengthy account of the life-history of the insect in all its stages. The nests may be found almost anywhere, provided that light and water are sufficiently excluded. The ants seldom burrow to any great depth in the ground and when they make burrows these are generally at the foot of tree-trunks or under the ridges in cane, cotton or corn fields, from 4 inches to 10 inches below the surface being the usual depth. These ants have a strong dislike to light; their sense of smell is exceedingly keen, but it is doubtful whether they possess the sense of sight or hearing, at all events to any considerable extent. Foraging ants have been found to travel about 145 feet per hour. The authors discuss the relations of the ant to other insects at length and give a list of scale-insects and aphids attended by the ants, with the trees on which they are found, and they say that these Homoptera are so thoroughly protected that it is very rarely that a ladybird is found at all on the infested tree. In one respect the ant is beneficial, in that it eats the sorghum midge Contarinia (Diplosis) sorghicola, Coq. Observations on the natural control of this ant have shown that a cockroach (Thyrsocera cincta, Burm.), which occurs in the southern United States, Mexico and Central America, eats it, but the number of ants destroyed by this insect is certainly inappreciable. Attempts were made to infest a nest with Pediculoides ventricosus [Pyemotes ventricosus], Newp., and the authors reared enormous colonies of these mites on larvae and then placed them in the formicaries, but found that although the mite had some effect, nothing approaching the quantity used was ever likely to occur in nature and the method was therefore useless. Attempts to infect colonies with the fungus, Sporotrichum globuliferum, yielded no practical results. The authors then go on to consider artificial methods of control and repression. Various proprietary and coal tar disinfectants were tried and it was found that none of these was effective for more than two days in preventing the travelling of ants. Oil of citronella seemed to be more distasteful and was effective so long as the odour remained, but it required constant renewal. Zeno-leum powder was quite effective. Pine tar, tobacco dust and sulphur were found to be of no use whatever. Bands of tanglefoot were only useful until a sufficient number of ants had been captured to form a bridge for the others. Crude petroleum was found to be on the whole the best repellent of all the liquids used. Tape soaked in a solution of corrosive sublimate and allowed to dry and fastened round the legs of tables, edges of shelves, &c., was effective for many months, provided it was kept dry. It is useless as a poison because the ants cannot be persuaded to touch their favourite foods when it is present in the proportion of 1 to 500. The extremely poisonous nature of the substance renders it difficult of application in households. Fumigation experiments are described and experiments with poisons of various kinds. Two or three protected saucers placed about a room or under tables bearing poisoned honey, meats, &c., would effectually rid the vicinity of ants in from one to three days' time, and it was further observed that they never returned in numbers so long as the dishes of po son were kept there. Methods of keeping the ants from apiaries are described and practically consist in placing the hives upon a table with weather-boarding round the sides to protect the upper part of the legs from wet and fixing round these legs bands of corrosive sublimate tape, and below them plates of sheet zinc about 6 inches square to prevent storm water from splashing upwards. The difficulties of control in orange groves are great, but it has been found that the spread of the pest can be effectively limited by digging ditches through the groves which are kept filled with water and making special provision to prevent the passage of the ants across the necessary bridges for transit purposes. Winter trap boxes were also found to be very satisfactory. These are rough boxes 2 ft. by 2 ft. by 3 ft. filled during the latter part of October with a mixture of cotton seed and dead grass. The top is left open so that the rain would wet the contents and start decay. By cutting down the standing grass and weeds in the orchard the ants appear to be driven into these trap boxes and can then be destroyed. Hydrocyanic acid was useless, but carbon bisulphide was found to be perfectly satisfactory for their destruction. The bulletin concludes with a lengthy bibliography dating from 1868..