They never venture in sight except in extreme cases. No one is ignorant of the terrible destruction these insects occasion to the works of man. Invisible to those whom they threaten, they push on their galleries to the very walls of their houses. They perforate the floors, the beams, the wood-work, the furniture, respecting always the surface of the objects attacked in such a manner that it is impossible to be aware of their hidden ravages. They even take care to prevent the buildings they eat away from falling by filling up with mortar the parts they have hollowed out. But these precautions are only employed if the place seems suitable, and if they intend to prolong their sojourn there. In the other case they destroy the wood with inconceivable rapidity. They have been known, in one single night, to pierce the whole of a table leg from top to bottom, and then the table itself; and then, still continuing to pierce their way, to descend through the opposite leg, after having devoured the contents of a trunk placed upon the table. On account of the devastations which they occasion, Linnæus has called the white ant the greatest plague of the Indies.
There exist in France two species of termites, the Termes lucifugus, a little insect of a brilliant black (at least in the male), with russety legs, which is common enough in the moors of Gascony; and the Yellow-necked White Ant (Termes flavicollis), which lives in the interior of trees and does a great deal of mischief in Spain and in the south of France to olive and other precious trees, whilst the first attacks oak and fir trees. Latreille established that it is the Termes lucifugus which causes such havoc at La Rochelle, at Rochefort, at Saintes, at Tournay-Charente, in the Isle of Aix, &c., where many houses have been completely undermined by these terrible insects. But M. de Quatrefages [114] has proved that the habits of the termes found in towns differ in many essential points from the habits of termes in the country. And so it is most probable that the former belong to an exotic species, which must have been unfortunately imported into France by a merchant vessel. According to M. Bobe-Moreau, [115] it was only in 1797 that termites were discovered for the first time in Rochefort, in a house which had stood for a long while uninhabited, and which they had completely undermined. In 1804, Latreille relates, as a "hearsay," that the termites had for some years made the inhabitants of Rochefort uneasy; but in 1829 the same author tells a very different tale. He speaks with dismay of the ravages committed by this insect in the workshops belonging to the Royal Navy. The importation of the termes into France is then of recent date. A note which was sent to M. de Quatrefages by M. Beltrémieux, fixes with still greater accuracy the date of the importation of the termites; it must have taken place about 1780, a period at which the brothers Poupet, rich shipowners, caused bales of goods to come from St. Domingo to Rochefort, to La Rochelle, and to other places in that neighbourhood which possess storehouses. The ravages which the termites have committed in the towns of La Saintonge are really frightful. Like Valencia, in New Granada, these towns will find themselves one of these days suspended over catacombs. At Tournay-Charente, the floor of a dining-room fell in, and the Amphytrion and his guests tumbled together in the cellar. There may be seen in the galleries of the Museum of Natural History of Paris the wooden columns which supported this room, and which were preserved by Audouin, who had been sent on a mission to report on the damages done. Audouin also selected, as an object of curiosity, a lady's bridal veil, which had been entirely riddled with holes by the termites.
At La Rochelle these insects took possession of the Prefect's house (built by the brothers Poupet), and of the Arsenal. There they invaded offices, apartments, court, and garden. They could not drive in a stake, or leave a plank in the garden, but it was attacked the next day. One fine morning the archives of the department were found destroyed, without there being the smallest trace of the damage to be seen on the exterior. The termites had mined through the wood-work, pierced the cardboard, eaten up the parchments and the papers of the administration, but had always scrupulously respected the upper leaf and edges of all the leaves. It was by mere chance that a clerk, less superficial than his colleagues, one fine day raised one of the leaves which hid this detritus, and thus discovered the destruction of the archives. All the papers of the Prefecture are now shut up in boxes of zinc.
These termites do not venture, any more than their congeners, into the light of day. These terrible miners always envelop themselves in obscurity, and construct on all sides covered galleries as they advance into a building. M. Blanchard and M. de Quatrefages saw in La Rochelle the galleries made by them. They are tubes formed of agglutinated material, which are stuck along the walls in the cellars and the apartments, or else suspended to the roof like stalactites. Certain parts of Agen and of Bordeaux begin also to suffer from the ravages of these insects. The danger appears to be imminent.
We are indebted to M. de Quatrefages for some interesting experiments on the termites of La Rochelle. Not only has the learned naturalist helped to make known to us the habits of these dark-loving insects, but he has also told us how to destroy them. Different substances have been tried in vain to stop these terrible ravages—essence of turpentine, arsenical soap, boiling lye, &c. M. de Quatrefages had recourse to gaseous injections. He tried successively binoxide of nitrogen, nitric acid, chlorine and sulphurous acid; chlorine, above all, fully answered his hopes. With pure chlorine he killed the termites instantaneously; mixed with nine-tenths of air, he suffocated them in half an hour. "For attacking the termites," says M. de Quatrefages, "one ought to choose by preference the period of their reproduction, so as to destroy the pregnant females. It is probable that, like their exotic congeners, the termites of France will endeavour to defend themselves by walling up the interior of their galleries at the first signs of an attack. The operator must then act with a great deal of promptitude, and direct the apparatus as much as possible into the very centre of their habitation, where the galleries are the broadest and the most numerous.
"With whatever care one acts, and whatever may be the success of a first attempt, it seems to me impossible to destroy in one campaign all the termites of a locality. In this, as in all operations of the same kind, a certain amount of perseverance is necessary, especially if it is in a town or in a country infested by them to a very great degree; in that case one will be forced to repeat the operation from time to time. When, on the contrary, the termites are already cantoned, it seems to me that the success ought to be lasting. This is fortunately the case at La Rochelle; and by knowing how to profit by it, one may doubtlessly prevent the spread of these pests, which at one time or another, may attack the whole town." [116]
In 1864 the Lords of the English Admiralty addressed an inquiry to the Entomological Society of London, on the best means of preserving wood from the attacks of the Indian termites. In answer to this inquiry, the Entomological Society recommended many processes: the injection of quicklime or of creosote, the application of arsenical soap, &c. But it does not appear that these processes are infallibly efficacious, nor, above all, easy to employ.
| Fig. 384.—Larva of Perla bicaudata. | Fig. 385.—Larva of a Nemoura. | Fig. 386.—Perla marginata (larva). |
Among other Neuroptera which undergo incomplete metamorphoses, we may mention, first, the genera Perla and Nemoura, [117] (Figs. [384], [385], and [386]), which flutter about the banks of rivers, and settle on stones, shrubs, and aquatic plants. Their larvæ are naked, without cases, and always live in the water, hiding themselves under stones, to watch for small insects, for they are carnivorous. One sees them often balancing their bodies, holding on to a pebble. They go through the winter, and only become pupæ in the spring. After moulting, they have the rudiments of wings. Very soon afterwards the pupæ leave the water, and undergo their metamorphosis. The adult lives only a few days, for its mouth is not suited for re ceiving food. The larvæ have, at the end of their bodies, two long threads, which remain in the perfect Perla, but not in the perfect Nemoura; the latter lose the two caudal hairs when they arrive at the adult state. One species of Perla is very common on the quays of Paris.