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Page:Popular Science Monthly Volume 65.djvu/320

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THE POPULAR SCIENCE MONTHLY.

Jose scale to his premises. Undoubtedly this scale insect came to this country in some such way on ornamental stock from North China.

 

The Asiatic Ladybird, the Natural Enemy of the San Jose Scale.

Throughout the region investigated in China where the San Jose scale occurs the natural agency keeping the scale in check was evidently a small ladybird (Chilocorus similis), which was feeding voraciously upon it wherever the scale was found in any numbers. A considerable quantity of these beetles was collected in both Japan and China and sent by mail to Washington. Unfortunately, most of the specimens died in transit or during the first winter. Two individuals, however, survived, and during the first summer from these two some five thousand or more beetles were secured. The original stock was kept in cages, but later on the insects were liberated in an experimental orchard attached to the insectary of the department. During the first summer a considerable number of colonies were sent out to various states placing them in charge, in the main, of the entomologists connected with the state experiment stations. During the summer of 1903, the second one since the introduction of this insect, some thirty or forty additional colonies were distributed. A good many of these colonies were liberated under rather unfavorable conditions, and the beetles probably perished. The best success has come from certain colonies sent to Georgia. One of these, located at Marshallville, presents a most satisfactory outcome. This orchard contains some 17,000 peach trees, covering about 85 acres, and has lying immediately adjoining it a much larger orchard belonging to the same owner, containing 250,000 trees, all scatteringly infested with scale. The ladybirds were liberated in August, 1902, in the smaller orchard. An examination of this orchard in July, 1903, indicated that the beetles were rapidly spreading and that they would soon cover the smaller orchard. A rough estimate at this time of the number of ladybirds in all stages places the total at somewhere between 25,000 and 40,000. In Georgia the beetles evidently continued breeding up to January. There is, therefore, in this orchard at least, a very flattering outlook for good results from the imported beetle. Other colonies placed where there were only two or three or but a few trees have not yielded very satisfactory results. This outcome is not especially surprising, as under such circumstances the beetles are very apt to fly away and become lost. We are endeavoring, therefore, to place colonies where there are rather Large bodies of trees infested with scales. After the beetle becomes once well established, distribution can be more general, but until this end is reached it is probably wiser not to waste material in sending specimens for colonization to small orchards or gardens or for liberation on a few trees. Tn Japan and China where the Chilocorus occurs rather generally, it finds food for itself in every dooryard, the white