OUR FRIENDS THE INSECTS BALDUF 437 



instrumental in transporting or disseminating such insects. It 

 occurs also that their parasites are not spread at the same time, 

 permitting the host to multiply to unprecedented numbers and to 

 greatly increase damage. The common asparagus beetle, a European 

 species, is capable of causing severe loss under favorable conditions. 

 In the East it is in part checked by a chalcid egg parasite, which, 

 as far as known from several attempts to locate it in Ohio and Illi- 

 nois, has not followed its host into all its present geographical range 

 in America. On the other hand, the squash bug, a native species 

 of general distribution, seems to be without its egg parasite in Illi- 

 nois, whereas such a species is known to exist in the eastern States. 

 Providing a more extended study of these and other insects should 

 confirm such findings as the above, the artificial spread of the para- 

 sites of these pests might be undertaken, and the parasites could 

 probably be established with little cost or difficulty. Deserts, moun- 

 tain ranges, or large bodies of water may act as deterrents or bar- 

 riers to the spread of parasites into the areas which may be reached 

 with relative ease by their hosts on account of their better equipment 

 for long-distance travel. 



The most obvious as well as most productive use that can be made 

 of parasites is based on the fact that some of our plant-eating in- 

 sects are of foreign origin. These have usually come to our country 

 without their natural enemies, hence multiply without limitations 

 and constitute some of our " millionaire " insect pests. A few major 

 examples are the European corn borer, the gypsy and brown-tai] 

 moths, the Japanese beetle, the codling moth, and the imported 

 cabbage worm. It has been recognized for about 40 years, since 

 the gypsy-moth problem became acute, that one of the fundamental 

 steps to take in attempts to control such imported and liberated 

 pests is to study them in their native situations. These studies soon 

 revealed that the insects were usually of relatively small importance 

 in their old homes and that this difference in their status was caused 

 by the work of one or more parasites. Thus was suggested the idea 

 of bringing these parasites to this country, where it was hoped they 

 would eventually perform the same good service as in their native 

 lands. The result is that many species of parasitic insects have 

 been introduced and successfully established here in the last four 

 decades and with more or less of the desired effect. 



The procedure in such introductions naturally varies much due to 

 the difference in habits of the parasites and their hosts and the 

 advantage taken of earlier experiences for development of better 

 methods of handling them. But the general essentials are as follows : 

 Specialists in parasitic insects are sent by the States or usually the 

 Bureau of Entomology of the United States Department of Agricul- 



