INSECTS INJURIOUS TO AGRICULTURE 409 



inally from Australia, where it had rendered inestimable service in 

 destroying mealy-bugs {Dactylopius, Eriococcus, etc.), and which, in- 

 troduced into the Hawaiian Islands, developed with a surprising rapid- 

 ity, comparable to that of Icerya in California. This ladybird is there 

 considered as one of the most important enemies of the scale insects of 

 the coffee plantations, and particularly Pulvinaria psidii, one of the 

 greatest enemies of this crop. Coccinella repanda is also naturalized 

 and is to-day one of the most common ladybirds, and most efficacious 

 among those which attack orange plant-lice and the plant-lice of 

 Hibiscus and sugar cane. 



In 1899, Koebele left for Australia and the Fiji Islands and made 

 numerous sendings of ladybirds and different parasites to the Hawaiian 

 Islands, notably to combat Ceroplastes rub ens Mask. 



At the end of 1902 the attention of planters was particularly di- 

 rected to an injurious leaf-hopper on the sugar cane, Perhinsiella sac- 

 charicida Kirk. It was introduced from Australia in about 1897 and 

 has since that time increased and spread and become a perfect plague 

 for this important crop. The attempts made to introduce living para- 

 sites in California at the expense of similar leaf-hoppers having given 

 unsatisfactory results, Koebele and Perkins left in the spring of 1904 

 for Australia, and during the course of that year sent to Hawaii a great 

 number of insects parasitic or predaceous, and among them a consid- 

 erable quantity of enemies of Perkinsiella. 



Considering that the money appropriated by the government was 

 insufficient, the Hawaiian Sugar Planters' Association did not hesitate 

 to advance important sums in order to further the study of the question, 

 and created itself a section of entomology in its experimental station, 

 and has started a series of investigations exclusively upon the enemies 

 of sugar cane and their parasites. Some remarkable monographs are 

 now in course of publication. 



The method of utilizing beneficial insects has been, during fifteen 

 years, used with such activity that the list of useful insects which have 

 been imported from one country to another, in order to combat the 

 plagues of agriculture, is already very long. 



We have already spoken of some of them in giving a resume of 

 Koebele and Compere. Omitting those which up to the present time 

 have given only uncertain results, or which have not succeeded in nat- 

 uralizing themselves, we will limit ourselves to a mention of some inter- 

 esting species, either because they have fully justified the hopes founded 

 upon their introduction, or because they appear likely to soon play an 

 important role in the struggle against the enemies of agriculture. 



Rhizooius in California. — Among the ladybirds must at once be 

 mentioned Rliizobius ventralis Erichs. This little ladybird, of a spe- 



