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Page:Popular Science Monthly Volume 65.djvu/311

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THE SAN JOSE SCALE.

gained lodgment in Europe so far, and the chances arc that it' it should do so the climate of Europe is so unfavorable that it would not be nearly so mischievous there as in America.

The explorations, which are briefly narrated in this paper, wen; undertaken to discover the native home of this scale insect, which was, prior to 1901, a mere matter of conjecture. The desirability of discovering the origin of this scale pest arose from the now well-known fad that wherever an insect is native it is normally kept in check by some natural means, and as a rule by some predaceous or parasitic enemy. In the chance importation of foreign destructive insects to our shores it very often happens that the natural check or enemy is left behind, and the imported pest becomes in consequence much more injurious here than in its native place. In a number of notable instances in this country very great benefit has been derived by the discovery and introduction of such natural enemies, thus reproducing the conditions which obtain in the native home of the injurious insect. The fluted scale and the Australian ladybird in California is the most notable instance. The importation of this ladybird from Australia has made citrus growing possible in California, and saves annually many millions of dollars to that state. This and other similar cases indicated the desirability of discovering the native home of the San Jose scale, and the importation, if possible, of whatever natural means were found there keeping it in check.

Prior to this investigation there was a pretty well founded belief, shared by Dr. Howard and the writer, that the San Jose scale was a native of eastern Asia. "Without going into detail, this belief was based chiefly on the ground that most other quarters of the world had been fairly well investigated without any evidence of this scale insect being found. It was known to occur in Japan, but the evidence rather indicated that it had been recently brought to that country from the United States in connection with the large shipments of nursery stock from California to Japan during the last twenty-five or thirty years. The itinerary, therefore, planned by the writer, with the advice of the chief entomologist of the Department of Agriculture, Dr. L. 0. Howard, was to include Japan, China and any other countries in eastern Asia which it should prove desirable to visit. Six months were devoted to a very thorough exploration of the different islands of the Japanese empire, and three months to China, with shorter periods in other regions. The explorations in China and Japan are the only ones which bear especially on the San Jose scale problem.

 

Explorations in Japan.

During the time spent in Japan, from April to September, 1901, the writer visited some forty-two provinces, and explored all the prin-