466 



Howard (L. 0.). The Practical Use of the Insect Enemies of Injurious 

 Insects. — Separate, no. 704, 1917, from Yearbook Dept. Agric, 

 Washington, D.C., 1916, 16 pp., 8 figs. [Received 7th August 

 1917.] 



This paper reviews some of the most successful instances in which 

 natural parasites have been introduced from their native country for 

 the control of some imported pest. The Australian ladybird 

 [Novius cardinalis), introduced into California to control Icerya (fluted 

 scale), has been the most successful of these experiments, while the 

 sugar-cane leaf-hopper {Perkinsiella saccharicida) has been largely 

 controlled in Hawaii by Paranagrus optabilis, introduced from 

 Australia, and the sugar-cane weevil-borer (Rhabdocnemis obscunis) by 

 a fly [Ceromasia sphenophori] from British New Guinea. The author 

 discusses the factors which contributed to the success of these intro- 

 ductions and points out that the problem of parasitisation is generally 

 a complex and difficult one, as in the case of the introduction and 

 establishment of Schedius kuvanae from Japan as a control of the 

 gipsy moth [Lymantria dispar], and of the European parasite 

 Parexorista cheloniae to control the brown-tail moth [Euproctis cliry- 

 sorrhoea]. This work has on the whole been successful and, while it 

 is almost certain that these two pests will spread further westward, 

 the imported natural enemies will go with them, and it is unlikely that 

 any such long-continued and disastrous outbreaks will occur as those 

 experienced in Massachusetts some years ago. When the silk industry 

 in Italy was threatened with extinction owing to the scale-insect 

 [Aulacaspis pentagona] infesting the mulberry trees, the parasite 

 Prospaltella berlesei, introduced from America and Japan, proved a 

 most successful control. 



Undoubtedly the future will see a considerable development of this 

 biological method of controlling insect pests, and particularly in 

 America, where more than one-half the principal crop pests have been 

 accidentally imported from other countries, it seems likely that many 

 successful introductions may be made of parasitic and predatory 

 insects, and in fact of all species that are beneficial to agriculture. 

 This would entail a great amount of biological study before the 

 experiments were made, and the benefits could only be derived 

 gradually. 



Burgess (A. F.). Suppression of the Gipsy and Brown-tail Moths and 

 its Value to States not infested. — Separate, no. 706, 1917, from 

 Yearbook Dept. Agric, Washington, D.C, 1916, 10 pp., 7 plates. 

 [Received 7th August 1917.] 



The history of the infestation of the gipsy moth {Lytnantria dispar) 

 and the brown-tail moth {Euproctis chrysorrhoea) in the United States 

 is reviewed in this paper ; the extent of the injury is described and 

 illustrated by photographs and the methods of dispersion are 

 discussed. The problem of introducing parasites for purposes of 

 control has resulted in 7 or 8 species having become established which 

 are helping to clear the States of infestation. The method of thinning 

 out the favourite host-plants of these pests from the woodlands is 

 dealt with [see this Review, Ser. A, v, p. 475], while every effort is 



