A few years ago the orange-groves in southern California became infested with a scale-insect, which threatened to ruin them and to bring orange-growing in that part of the land to an unprofitable end. The matter received the careful attention of the chief entomologist of the United States Department of Agriculture, the lamented Professor C.V. Riley. In the course of the studies which he and his associates prosecuted, it was ascertained that the same scale-insect which was ruining the orange-groves of California is found in the orange-groves of Queensland, but that in Queensland this insect did comparatively small injury to the trees. Investigation disclosed the fact that in Queensland the scale-insect was kept down by the ravages of a parasitic insect which preyed upon it. This parasite, by order of the chief entomologist, was immediately imported, in considerable numbers, into southern California, and let loose among the orange-groves. The result has been most beneficial. These are two illustrations, from among hundreds which might be cited, of the very practical value of entomological knowledge. +--------------------------------------------------------------+ | | | EXPLANATION OF PLATE XXXI | | | | 1. _Lycæna pseudargiolus_, Boisd.-Lec., | | var. _lucia_, Kirby, ♂. | | 2. _Lycæna pseudargiolus_, Boisd.-Lec., | | var. _marginata_, Edwards, ♂. | | 3. _Lycæna pseudargiolus_, Boisd.-Lec., | | var. _marginata_, Edwards, ♀. | | 4. _Lycæna pseudargiolus_, Boisd.-Lec., | | var. _nigra_, Edwards, ♂. | | 5. _Lycæna pseudargiolus_, Boisd.-Lec., | | var. _violacea_, Edwards, ♂. | | 6. _Lycæna pseudargiolus_, Boisd.-Lec., | | ♂. | | 7. _Lycæna pseudargiolus_, Boisd.-Lec., | | ♀. | | 8. _Lycæna pseudargiolus_, Boisd.-Lec., | | var. _neglecta_, Edwards, ♂. | | 9. _Lycæna pseudargiolus_, Boisd.-Lec., | | var. _neglecta_, Edwards, ♀. | | 10. _Lycæna pseudargiolus_, Boisd.-Lec., | | var. _piasus_, Boisduval, ♂. | | 11. _Lycæna dædalus_, Behr, ♂. | | 12. _Lycæna dædalus_, Behr, ♀. | | 13. _Lycæna heteronea_, Boisduval, ♂. | | 14. _Lycæna heteronea_, Boisduval, ♀. |