DESTROYERS OF INSECT PESTS^ 79 



mons first settled in Utah, their crops were attacked 

 by the crickets and nearly destroyed, until the gulls 

 came in large numbers and preyed upon the crickets 

 and saved the remainder of the crops. In commem- 

 oration of this, a monument to the gulls has recently 

 been erected in Salt Lake City. 



Outbreaks of locusts in the Middle West have been 

 controlled by birds. A serious outbreak of the forest 

 tent-caterpillar occurred in New York and New Eng- 

 land in 1897-98, but was finally brought under con- 

 trol by the action of the birds. An outbreak of the 

 canker-worm occurred in an apple orchard in Illi- 

 nois. A study of the birds found here showed that 

 twenty-six kinds of birds were feeding on these 

 canker-worms, which formed thirty-five per cent of 

 the birds' food. There are many other records of 

 small local outbreaks which have been controlled by 

 the birds. But yet the greatest service that the birds 

 render is in keeping the insects down to such a point 

 that outbreaks do not occur. 



Division of labor. The division of labor in those 

 places where insects are found is well apportioned 

 among the birds. Some birds, like the sparrows, feed 

 upon the insects found on the ground; the wood- 

 peckers spear those in the bark and wood of trees; 

 warblers and vireos glean the small insects found on 

 the leaves, while the larger birds, like the cuckoos, 

 feed upon the larger insects found on the foliage; the 

 swallows prey upon the insects in the air. 



