10 INSECTS OF ECONOMIC IMPORTANCE 



of the downy woodpecker, a very large percent of 

 the food of warljlers, 95% of the food of the house 

 wren, and 96% of the food of the flycatchers. 

 Three hundred to five hundred insects have been 

 found in the stomach of one bird. 



The mobihty of birds makes them very efficient. 

 Forbes showed that in orchards where canker- 

 worms were abundant birds became abnormally 

 plentiful. 



Flycatchers and swallows live upon flying insects, 

 while robins and meadowlarks catch ground insects. 

 Cuckoos, orioles, warblers, and vireos devour leaf- 

 eating insects while nuthatches, titmice, and creep- 

 ers explore trunks of trees for small insects. 



References on the ivork of birds: 



Henshaw — U. S. Dept. Agri., vearbook 1907, p. 



165. 



Beal — U. S. Dept. Agri., yearbook 1908, p. 343. 



Sanderson — New Hamp. Expt. Sta., 19th and 

 20th Rpts., 1908, p. 398. 



Forbush — Useful Birds and their Protection. 



Introduction of predaceous insects — Preda- 

 ceous insects, especially ladybird beetles and cer- 

 tain ground beetles are sometimes introduced into 

 a locality to prey upon injurious insects. For ex- 

 ample, the Australian ladybird {Noviiis cardinalis), 

 the ground beetle (Calosoma sycophant a), and the 

 convergent ladybird (Hippodamia convergens). 



Introduction of parasitic insects — Parasitic 

 insects are introduced into one country from an- 

 other to help in the fight against insect pests. For 

 example, the many parasites introduced from Eu- 

 rope to prey upon the gypsy and brown-tail moths. 



Artificial methods 



Artificial methods consist mainly in the use of 

 insecticides. 



