WHOLE VOL. APPLIED ENTOMOLOGY HOWARD 533 



Nebraska, on an experimental reforestation area in the sand hill 

 country. The reforestation is in the Nebraska National Forest, and 

 the work is being done by the United States Forest Service. With 

 the coniferous trees used in this experiment, an eastern injurious 

 insect, one of the so-called tip-moths (Rhyacionia fntsfrana), was 

 accidentally introduced and flourished to such an extent as to threaten 

 the death of all the young trees. In the East an Ichneumonid parasite 

 (Canipoplc.v friistranac) was known, and colonies of this parasite 

 were taken from East Falls Church, Virginia, to Halsey, Nebraska, 

 and liberated in the infested area. Doctor Craighead, in charge of the 

 forest insect work of the United States Bureau of Entomology, 

 reported in the summer of 1929 that in the areas where the parasite 

 was first liberated parasitism had increased to as much as 80 per cent 

 and the percentage of destroyed tips had decreased from 90 per cent 

 to less than 30 per cent ; a definite improvement in the appearance of 

 the trees was discernible, and there was promise that the parasite 

 would be the solution of the very difficult problem. Later information 

 confirms that promise. The expert in charge of the work, to whom 

 much credit should be given, is Mr. Lynn G. Baumhofer of the Forest 

 Insects Section of the Bureau of Entomology. The trees planted on 

 the area were largely Austrian, Scotch, and yellow pine. 



The extraordinary work that has been done in several parts of the 

 world with Trichograinmaininutum, an egg-parasite of a large number 

 of injurious insects, has attracted great attention of late years. The 

 mass breeding of this useful parasite has been carried to an extreme 

 in southern California by Mr. Stanley Flanders who has simplified 

 and economized the work by using one of the common meal moths as 

 a breeding stock, the resulting parasites being distributed to walnut 

 growers to parasitize the eggs of the codling moth. Moreover, 

 Mr. E. R. Speyer, who has been studying the greenhouse white fly in 

 England for several years, has reared one of its parasites (Encarsia 

 formosa) on a very large scale for distribution to greenhouses in the 

 early part of the season at a time when fumigation would injure the 

 younger plants. 



This sort of work, verging upon the actual domestication of bene- 

 ficial forms, is undoubtedly important and will assume more im- 

 portance as time goes on. 



This whole question of the practical use of parasites and predatory 

 insects is considered by Dr. W. R. Thompson in a just-published 

 paper entitled " The Principles of Biological Control " (The Annals 

 of Applied Biology, May, 1930, Vol. 17, No. 2, pp. 306 to 338). 

 Doctor Thompson has been working upon problems of this nature for 



