USEFUL PARASITES

Evening Post, Volume CX, Issue 52, 29 August 1925, Page 8

USEFUL PARASITES

THE ROTHAMSTED CLEARING

HOUSE

PLAGUE DESTROYERS FOR THE

EMPIRE.

(FROM OCR OWN' CORRESPONDENT.)

LONDON, 9th July.

A correspondent of the "Sunday Observer" tells an interesting story of what is being done at the Rothamsted research laboratory for the relief of sufferers from insect, fungus, and other pests all over the Empire.

Waiting of the parasites sent out to New Zealand for the purpose of destroying earwigs, the correspondent says: "Now the earwig is very careful of its eggs. Its brooding of them is queer and comic as well as unusual. The mother 1 crouahes over her eggs as carefully as a hen, but, nevertheless, has no defence against the parasite, which leaps upon the egg as soon as it is laid and destroys its fertility in the usual way, by converting it into food for its own grub. As soon as the parasites were found, they were cultivated with extreme care by the entomoligists of Rothamsted. It was a liberal education in the new science to see the breeding of the minute creatures, the care" expended on giving them the right temperature and right light; and, above all, on the screening of their dormitories, so that the parasites that preyed on the parasites (for these, too, were discovered) could not find an entrance. It was little use breeding a mere battalion for this warfare. The creches and cages were multiplied; and the parasites increased at so satisfactory a rate that presently a division, a corps, an army of them wGre ready' for export to the Antipodes. "How they will fare when let loose in the open, upon the earwigs of New Zealand, remains to be seen. Will they' stand the climate? Will they escape the ministrations of their own 'lesser fleas'? Will they maintain their ancestral instincts? It is delicate work. Such standard examples in bigger genera as the suppression of rats by the mongoose in the West Indies, reveal the danger of tampering with such things; but in regard to these insect parasites, the apaprent danger usually carries its own cure. For example, a young man of science, . who directed an admirable little laboratory in Queensland—a miniature 'local Rothamsted— journeyed to South America to discover an enemy of the 'pricldy pear,' and found one fly which could sting to death even this invincible weed, that eats up tens of thousands of acres a year. His high hopes were, however, dashed, because it appeared in the sequel that the fly only attacked one variety of the plant, and that one of the less offensive and prevalent. But the point of* present emphasis is that the parasite and the plant disappeared simultaneously. The parasite, in short, cannot live without the host. In wellregulated countries, such as England, a balance is usually reached. ■ CLEABING HOUSE OP PLAGUE DESTROYERS. "England—especially Rothamsted, in Herefordshire—is becoming a sort of clearing-house for the plagu* destroyers. A very pretty instance has occurred in relation to Africa. A., supposed parasite of the tsetse fly, perhaps the worst of all the enemies of agricultural, and so of human, progress in Africa, was discovered in West Africa, and was greatly desired by East Africa. But the trans-continental railways are not yet surveyed; and as the parasites .insist on going through some fairly rapid metamorphoses, needing favourable conditions, there seemed to be no way of transferring them safely across tha continent. They needed too much care during the. crisis. The solu- j tion was found by conveying the animals Rothamsted, where they break the journey for a generation or so. In that sanctuary they undergo their cycle of changes, and tho next generation is exported from Engliinrl <o East Africa. How far the remedy will 'prove sovereign has yet to be known, but the method is the most promising of all methods,- and its possibilities are being very rapidly and thoroughly explored In Britain tho Ichneumon, with tho exception of tho ladybird, is the most deadly enemy of most blights, for example, tlio very prevalent bean Might; Jutt, as in Uig case of the earwig, the established relationship is rather harder lo break in Kngland than in countries that have a. tendency to greater extremes. It is thought,- for example, | that a considerable success has already, after less than two years' trial, followed the introduction of a parasite into that tittle gem of the Empire, Fiji. With- j in a year after Thecla—such is its name —whs released, it had spread widely, and was beginning its deadly but beneficent ministrations in the suppression-J oi the Lautan.a plagua.." I