Feb. 1907.] 



107 



Plant Sanitation. 



Australia, parts of Germany and Switzerland large numbers of parasitized full- 

 grown larvae and pupae of the gypsy moth to Boston. From these specimens were 

 reared six distinct species of parasites, and of these about 500 puparia of Tachma 

 larvarum, one of the largest and most important of the European parasites, were 

 secured and kept for overwintering in an apparently healthy condition. Numerous 

 specimens of a smaller Tachma fly were also secured. The other parasites from 

 these particular sendings were unimportant. Arrangements were made in Europe 

 with a large number of experienced collectors and with the official entomologists 

 of different countries, so that the work of sending parasitized specimens over to 

 America will be continued systematically for two years to come. The work of 1905 

 has shown that it is an easy matter to import these parasites in living condition, and, 

 with the abundance of food which they will find in Massachusetts, there can be little 

 doubt that they will establish themselves and will rapidly increase, eventually bring 

 ing about the the same condition of natural equilibrium that exists in Europe. 



The assistance and co-operation of official European entomologists were 

 readily gained, both on account of their general interest in such matters and of 

 the fact that the United States can be of use to their countries in a similar way. 

 Thus already, the speaker stated, he had shipped sendings of Diaspis pentogona 

 and Mytilaspis citricola to official entomologists in Italy and France in the hope 

 that American parasites of these species will issue on European soil.* 



It will appear from what has been said that some excellent results have 

 been obtained in this introduction work. Very many experiments have resulted 

 negatively, and many of the insects imported have not proved to be of great success 

 but every natural enemy of an injurious species, once established, is more or less 

 of a help in the warfare against the pest. When a great success is achieved like 

 that of the introduction of the Australian ladybrid or the African Scutellista, 

 the saving which results far more than compensates for the expenses of long 

 continued travel and investigation. 



Finally, it must be stated that in experimental work of this kind, when 

 conducted by the right men, there is no danger. The historic cases of the introduc- 

 tion of the English sparrow into the United States, of the East Indian mongoos 

 into the West Indies, and of the European rabbit into Australia, are often mentioned 

 in connection with these importations of beneficial insects and as warnings. But 

 parasitic insects are always parasitic upon other insects and nearly always upon 

 injurious species. Predatory insects are always predatory upon other insects. 

 There is not the slightest danger that any of these importations will become des- 

 tructive to agriculture except in the indirect way in which a secondary parasite, 

 by destroying a primary parasite, may thus liberate an injurious insect from 

 attack. Persons engaged in this work, therefore, should be able readily to distin- 

 guish between primary parasites and hyperparasites. 



Referring in conclusion to the importation of the natural enemies of the 

 gypsy moth and brown-tail moth, the speaker stated that the prospects on the 

 whole are favorable for eventual relief. He stated, however, that this relief will 

 not be speedy, and property holders in the infested regions must not relax their 

 efforts to keep the injurious insects down. Observations during the past years 

 have shown that the complete defoliation which results from the attacks of the 

 insects will kill certain varieties of trees in two seasons, and if work against the 

 insects is remitted while waiting for the parasites to develop, the consequent loss 

 will be very great. 



* During the winter of 1905-06, 110,000 nests of the browntail-moth were brought over from 

 many different localities in Europe. These were installed in the laboratory at Saugos, and at the date'of 

 writing over 40,000 primary parasites have issued and are being colonized in the vicinity of Boston. L.O H 

 May 31, 190G. 



