80 BOARD OF AGRICULTURE. [Pub. Doc 



act in this State is an encouraging sign of the times, show- 

 ing the drift of popular sentiment. The enhanced value 

 now placed upon shade trees leads naturally to an increased 

 appreciation of the damage wrought by shade-tree insects, 

 — an interest bound to grow with the increasing concentra- 

 tion of population in cities and their suburbs. 



Of three principal factors directly favoring an increase in 

 insect depredations of shade trees, one of the most impor- 

 tant is the massing throughout large areas of a single species 

 of tree, in accordance with the modern dictum "that every 

 connected street must be planted with a single variety of 

 tree." Insects are more or less critical in matters of diet, 

 the tent caterpillar preferring the wild cherry, the elm- 

 beetle the various species of elm, the brown-tail moth the 

 pear, and so on throughout the list. Where the chosen 

 food plant of a particular insect has been planted in large 

 numbers, there that species finds just the best conditions for 

 its rapid development. The " City of Elms'' must be of 

 necessity the city of elm insects. Boston Common gives a 

 more familiar illustration. The older plantings are almost 

 entirely of the American and English elms. The white- 

 marked tussock moth finds in the foliage of the elm food 

 exactly suited to its development : hence this insect has 

 periodically stripped these elms at least from the days of 

 Harris to the present time, its ravages being ultimately 

 checked Irv the increase of its parasites. 



Another factor which has contributed in no small degree 

 to recent outbreaks of shade-tree insects is the superabun- 

 dance of the English sparrow, a seed-eating bird, pugna- 

 cious, filthy in habit, and of but little practical value as a 

 destroyer of insects. This bird thrives best where popula- 

 tion is most dense, and this is just the condition under 

 which shade trees have the hardest struggle for life. Im- 

 mensely prolific, and finding an abundant food supply in the 

 form of offal and refuse, the sparrow has directly or indi- 

 rectly eliminated the native birds which formerly inhabited 

 our city trees and fed upon injurious insects. We need not 

 seek far to find an illustration of the harm wrought by this 

 bird. In Northampton and vicinity the sparrow lias largely 



