CORRESPONDENCE.
THE LATEST INVASION OF ENGLAND.
Fro THE EDITOR OF THE "SPECTATOR."] SIR,—We look to fleets and armies to protect us from the inroads of human enemies, but other means must be adopted to secure us against smaller, but hardly less dangerous foes, some of which, as we learn from the newspapers of the present week, have already succeeded in gaining an unsus- pected footing on our shores. To the younger members of the community the announcement that the Colorado beetle has been found swarming in a potato-field at Tilbury will probably seem an announcement of no great importance, but older persons will remember the alarm felt throughout Europe about 1877, when this destructive insect, which was discovered in the Rocky Mountains in 1824, and commenced its march eastwards about 1859, had spread itself over the greater part of temperate North America, almost annihilating the potato crop in many places, and having reached the Atlantic seaboard, was expected soon to cross the ocean into Europe. At that time many reports of its appearance in England, Ireland, Sweden, Germany, were put in circula. tion. but a large proportion of these were fabulous, and some were absurd in the extreme. Not only were such dissimilar insects as the great green caterpillar of the death's head hawk-moth (which does feed on potatoes) mistaken for them, but on one occasion a marine creature like a large woodlouse, found running along a tow-rope at the docks at Dublin, was secured, and actually announced in the papers as a Colorado beetle ; the finder, a than a good position in society (a legal gentleman, if I am not mis- taken) having apparently supposed that he had arrested the beetle in the very act of landing from America! The onlY serious appearance of the beetle in Europe, however, prelim° to its recent discovery at Tilbury was at Miilheim, on the Rhine, a town about two miles from Cologne, but on the opposite bank of the river. How the beetle was introduced unknown, but, just as at Tilbury, it was discovered swarming in a potato-field. The authorities did not wait a moment, batroleum, t ordered the whole field to be ploughed up, drenched with
and burned over. These drastic measures were
pe eessful, and the pest disappeared; but there is little doubt that if any delay had occurred, the insect, which is very strong on the wing, might easily have spread on the Continent as it had previously done in America, until stopped either by adverse climatic conditions or by insurmountable natural barriers, such as mountains or oceans. The exact measures taken by the Board of Agriculture have not been published, but it is to be hoped that they will prove equally efficacious. There is good reason to hope so, for all the crops and grass within the infected area have been destroyed, and the sur- rounding neighbourhood was afterwards searched in vain for any traces of the insect. The beetle itself is rather larger than a ladybird, and the wing-cases are marked with alternate longitudinal stripes of black and yellow. From this it derives its scientific name of Doryphora (or Leptinolarva) decendineata. It is still more easily recog- nised by the red wings, an unusual character in beetles; but these are hidden under the striped wing-cases when the insect is at rest. The immature insects, which are of course wingless, are thick yellow grubs, with a row of black spots on each side. The yellow oval eggs are deposited in clusters on the under- surface of the potato leaves. Among their other evil qualities these insects are highly acrid, like many other leetles. Nevertheless, they are preyed upon by a number of other insects. After 1877 the beetle has been occasionally very destructive in America, the usual remedy recommended for its ravages being to spray the infected plants with a preparation of arsenic known as Paris green. But the Americans have become used to its ravages, and other insects, such as the gipsy moth, now usurp the attention which used to be given to the potato beetle in publications on American agricultural entomology. The gipsy moth to which we have just alluded is a striking instance of the danger of allowing a mischievous insect, however introduced, to establish itself in a foreign country; a danger all the greater because the natural enemies which keep it in check in its own country (parasitic ichneumons, S.:c.) are hardly likely to migrate with it to a new one. The gipsy moth is a well-known and destructive European insect, which formerly inhabited England, but is believed to be now extinct, though it is still very abundant on the Continent. Some time since an entomologist living near Boston, who had been rearing various moths from Europe and other countries, allowed a colony of the gipsy moth to establish itself in his garden. Presently the cater- pillars ravaged the whole neighbourhood, and after spending large sums annually for some time in trying to destroy them, the State of Massachusetts has now given up the task as hopeless. Possibly the effort might have been successful if the danger had been foreseen and grappled with at once, as in the case of the potato beetle. Under the provisions of the Destructive Insects Act every person meeting with a specimen of the beetle in any of its stages is bound under a penalty of £10 to notify it to a police constable, who must at once inform the local authorities, who must telegraph to the Board of Agriculture. Besides this, any person keeping or selling a living specimen of the beetle in any of its stages is liable to the same penalty of £10. These regulations are still in force, as are also probably similar legislations which were enacted in most of the Continental States about the same time. Con- sidering the great and permanent injury which the beetle may be expected to cause should it eventually establish itself in Europe, no reasonable measures of precaution can be looked upon as excessive or unnecessary.-1 am, Sir, Szc., W. F. KIRBY.
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