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POPULAR SCIENCE MONTHLY

the world of a practitioner, launched by his government into the search for the parasites of a fly, it is to show the vogue which the use of beneficial insects in the struggle against injurious insects enjoys in certain countries.

What will be the result of this experience? It is premature to express an opinion on the subject. The time necessary for the definite acclimatization of a parasite, and above all for it to multiply sufficiently to restrain the insect which it is its mission to attack, must be extremely variable, according to the species and also according to the extent of spread of the plague. It is only necessary for some months to elapse in the case of Novius cardinalis, but years may be necessary for such parasites as the Ichneumonids.

Utilization of Beneficial Insects in the Hawaiian Islands.—Journeys of Koebele.—The method of which we are speaking has nowhere been applied in a more extensive way than in Hawaii. These islands, ever fertile, present, as is well known, a climate extremely favorable for large number of tropical and subtropical crops. At the beginning of the American colonization, the only plants of economic importance were yams and cocoanuts, but since that time enormous numbers of useful plants, coming from all parts of the world, have been acclimatized in this rich country, and with them also have unfortunately been imported a large number of their natural enemies, among them, and the most important, scale insects and plant lice. It has been stated that the Hawaiian Islands are the paradise of these insects, since they are represented by numerous species coming from all parts of the world, which prosper there and flourish.

After having seen, in 1890, their orange and lemon trees relieved from Icerya by Novius cardinalis, the planters directed their efforts to this method in order to combat other agricultural plagues, and particularly the enemies of coffee and sugar cane.

They, therefore, gave Mr. Albert Koebele a commission to undertake this work. This entomologist, celebrated for his discovery of Novius cardinalis, and already employed at the same time by the State Board of Horticulture of California upon a similar mission, commenced by sending from California the Coccinellids which seemed most desirable for Hawaii, notably: Hyperaspis undulata Say, Scymnus debilis Lec, Chilocorus bivulnerus Muls., Rhizobius ventralis Er., and R. lophantæ Blaisd. The two latter became naturalized and constituted a useful resource for the country.

In 1893 he visited the islands and left immediately for Australia. From 1894 to 1896 he journeyed through Australia, China, Ceylon and Japan, and made during this journey numerous sendings of this insect to Hawaii and California. Among the best of these must be mentioned, in the first place, Cryptolæmus montrouzieri Muls., orig-