TIMBER: FORESTRY 411 



them in water to destroy the insects before the new crop of 

 beetles emerges from under the bark the following June. 1 



One of the most effectual means of destroying some injuri- 

 ous insects consists in introducing into the region where they 

 abound parasitic or other insects which will kill great numbers 

 of the objectionable species. Plant lice, for instance, are thus 

 killed by ladybugs. Vigorous attempts are now being made 

 to exterminate the gypsy moth in New England by means of 

 parasites and by carnivorous insects which attack and kill the 

 moth at some stage of its existence. The caterpillars of this 

 moth are extremely destructive to many kinds of trees, which 

 they strip of their leaves in a short time. More than $1,000,- 

 000 have probably been expended in Massachusetts alone in 

 trying to get rid of this pest. The moth was introduced into 

 America in 1869 by a scientist who lived at Medford, near 

 Boston, in the course of some most unfortunate experiments 

 on silk-producing insects. 2 



(7) Cattle should not be pastured in woods in which it 

 is important to protect the growth of young seedling dicoty- 

 ledonous trees. They do not greatly injure mature trees. 

 Sheep pasturing and forestry cannot thrive together, since by 

 browsing the sheep destroy many young seedling trees. On 

 grassy hill and mountain sides sheep, by close grazing and by 

 cutting the turf to pieces with their sharp hoofs, soon kill the 

 grassy cover and pave the way for extensive erosion. Great 

 damage has been done in this way in the Rocky Mountain 

 and the Pacific slope regions of our own country. In south- 

 ern Europe pasturing sheep and goats has led to the conver- 

 sion of great areas of comparatively fertile mountain sides 

 into bare ridges and bowlder-lined torrent beds. 



1 See " Insect Enemies of the Spruce in the Northeast," Bulletin 28, New 

 Series, Division of Entomology, U. S. Dept. Agr. 



2 "The Gypsy Moth in America," Bulletin 11, New Series, Division of 

 Entomology, U. S. Dept. Agr. 



