690 



AMERICAN FORESTRY 



kinds, sometimes in enormous numbers. 

 They are preyed upon by most small 

 birds, and particularly by the chipping 

 sparrow, goldfinch, house finch, Audu- 

 bon warbler, orange-crowned warbler, 



Her.mii Thrush and Wood Thrush 



both of these birds deserve a high place among those who destroy 

 insect enemies of trees. they feed largely upon these insects 

 and are also noted for their flute-like tones 



downy woodpecker, Baltimore oriole, 

 chickadees, bush-tits and kinglets. 



Another group of small but neverthe- 

 less very destructive insects are the 

 scale insects. These inconspicuous and 

 far from edible-looking creatures were 

 once thought to be free from the 



attacks of birds, but now more than 

 sixty species of birds are known to 

 prey upon them. The beautiful rose- 

 breasted grosbeak feeds upon a large 

 number of destructive insects, among 



them several species 

 of scales. More than 

 100 scale insects 

 have been found in 

 a single stomach of 

 this bird. Related 

 grosbeaks, the cardi- 

 nal, and the black 

 headed grosbeak also 

 are fond of scale 

 insects. Eighteen 

 per cent of the entire 

 food of 120 black- 

 headed grosbeaks 

 consisted of black 

 olive scales, pests 

 which are exceeding- 

 ly abundant and des- 

 tructive in C alif or ni a . 

 Twenty-nine species 

 of birds are known 

 to prey upon them. 

 The little bush-tits 

 depend upon scales 

 for about a fifth of 

 their whole subsis- 

 tence. 



Another insect 

 which injures trees 

 and which should 

 not be passed un- 

 mentioned is the 

 periodical cicada or 

 seventeen-year loc- 

 cust. These insects 

 deposit their eggs in 

 twigs, which either 

 die and drop off, or 

 heal with large scars. 

 The natural enemies 

 of cicadas are legion, 

 including practically 

 all carnivorous an- 

 imals. Among ver- 

 tebrates, fishes and 

 tortoises, when they have opportunity, 

 frogs, toads, lizards, squirrels, and a 

 multitude of birds prey upon the cica- 

 das. The English sparrow especially is 

 a persistent foe of this insect, and in 

 many cases it has been observed that 

 where sparrows are plentiful, hardly 



