OUR FRIENDS THE INSECTS BALDUF 439 



be of minor importance as factors in host control. Success depends 

 on so many influences that the entomologists concerned need have 

 intimate knowledge of every phase that composes the parasite's en- 

 vironment as well as of its habits and development. However, in 

 spite of failures due to inadequate facts, the specialists who are close 

 to the work are oj^timistic for the future, and Dr. L. O. Howard 

 (2, p. 282) says " work of this kind is in its infancy, and its 

 possibilities are great." It is necessary to point out again, however, 

 that this method of combating insect pests is not advocated as a 

 panacea for all insect troubles, and can not be regarded as a solitary 

 substitute for any or all other methods now in use. 



INSTANCES OF PARASITE TRANSPORTATION 



The transportations of parasitic insects have by no means been 

 to the United States alone, although this country started this type 

 of work on a large scale. Porto Rico imported experimentally in 

 1911-1913 from our own State certain wasp parasites {Tiphia sp.) 

 for the control of the sugar-cane grubs which are related to the 

 Illinois corn-root destroying white grubs. 



The mulberry scale threatened the silk industry in Italy (3), but 

 it was almost completely freed of this pest by a minute parasite 

 {Prospaltella herlesei) established there from America and Japan. 



Australia inadvertently received the woolly apple aphis, a notori- 

 ous louse pest of the apple, because its covering of woolly secretion 

 protects its body against ordinary contact sprays. The apple indus- 

 try had prospered greatly in that favorable country until the arrival 

 of this aphis. Professor Tilly ard, of Australia, with the aid of 

 our entomologists, received importations of a small wasplike para- 

 site from the United States where it holds this pest in check. The 

 parasite is flourishing in Australia, and, as a result, the apple indus- 

 try is doing the same. 



The larch forests of Canada have been severelj'' injured by an- 

 imported sawfly, whose larva eats foliage. About 14 years ago, 

 one of its foreign parasites was established, and by gradually increas- 

 ing has now practical control of the host, the last reports indicating 

 over 70 per cent mortality due to the parasite. 



The Hawaiian islands present a peculiar biological situation in 

 that they originally harbored few native crop pests. By interna- 

 tional commerce the sugar cane leaf hopper became established 

 there, and created heavy losses amounting in 1903 to $3,000,000. 

 By 1906 some species of egg parasites obtained in Australia were 

 multiplying rapidly, and after 10 years Doctor Howard (3, p. 7) 

 found that the leaf hoppers had been reduced to practical insignifi- 

 cance. This is only an example of numerous other instances of com- 



