104 



[Feb, 1907. 



PLA&T SANITATION. 



ON THE IMPORTATION OF BENEFICIAL INSECTS FROM 

 ONE COUNTRY TO ANOTHER. 



There are many large groups of insects which are parasitic in their habits 

 and which destroy other insects. There are other large groups which are predatory 

 in their habits and feed upon other insects. There is hardly an injurious insect 

 which does not have its natural enemies in its own class. Sometimes the natural 

 enemies will have the upper hand and the injurious species will be greatly reduced 

 in numbers. Again the natural enemies will be reduced and the injurious species 

 will abound. Wherever an injurious insect exists under normal conditions and in 

 its original home, its natural enemies as a rule keep it in check and prevent its 

 unlimited multiplication. But now with the large scale expansion of agriculture 

 and horticulture, and with the constantly increasing rapidity of traffic between 

 countries, it has frequently happened that injurious insects have been introduced 

 from one country to another without their natural enemies, and have consequently 

 multiplied to an enormous degree. The United States has suffered especially from 

 accidentally introduced insect pests mainly coming from Europe. About one-half of 

 the injurious insects of first-class importance now existing in the United States were 

 accidentally introduced from some foreign country. 



A great interest in the handliug of insects by means of their natural enemies 

 has constantly been increasing in many parts ot the world since the year 1888 when 

 the strikingly successful search for the natural enemies of the fluted scale (Icerya 

 purchasi) was begun under the auspices of the United States Department of Agricul- 

 ture. But the idea was an old one. Dr Asa Fitch, formerly the State Entomologist 

 of New York, was probably the first entomologist in America or elsewhere to 

 take this question into serious consideration. In 1854, following a disastrous attack 

 upon the wheat crop of the eastern United States by the wheat midge (Diplosis 

 tritici), a species accidentally introduced from Europe during the early pai't of that 

 century, Doctor Fitch made a careful study of the insect both in this country and 

 from the European records, and was impressed with the fact that in Europe the 

 insect in ordinary seasons did no damage, and that when occasionally it became so 

 multiplied as to attract notice it was a transitory evil which subsided soon. He 

 compared the insects taken from wheat in flower in France with those taken from 

 wheat in flower in New York, and he found that in France the wheat midge consisted 

 of but seven per cent of the insects thus taken while its parasites consisted of eighty- 

 five per cent ; whereas in New York the wheat midge formed fifty-nine per cent of 

 the insects captured and there were no parasites of which he could be certain. He 

 then came to the conclusion that it was a question of introducing the parasites into 

 the United States, and he made an effort by correspondence with English entomolo- 

 gists, which however was a failure owing to the fact that he was unable to enlist the 

 active co-operation of his correspondents. 



Later William LeBaron, State Entomologist of Illinois, attempted to 

 transport a parasite of the oyster-shell bark-louse of the apple from one part of the 

 State of Illinois to another part of the same State where the parasities seemed to be 

 lacking. Some slight success was reported, but the parasite subsequently proved to 

 be one of general American distribution- Another international attempt was made 

 in 1873, when Planchon and Riley introduced an American predatory mite into 

 France. The mite was an enemy of the grapevine Phylloxera, and became established 

 in France, but produced no appreciable results in the way of checking the pest. In 1874 



