BLACKHEAD VS. SCALE INSECTS. 



73 



Fig. 35. — Spring cankerworm 

 (Paleacritavernaia). (From 

 Riley, Bureau of Entomol- 

 ogy,) 



the other group (Homoptera), including leaf and tree hoppers, plant 

 lice, and cicadas, was distributed among 9 of the grosbeaks examined, 

 and composes a little more than 0.5 percent of the total food. Next 

 is the family of scale insects (Coccidse), which from an economic 

 standpoint is the most important element of the black-headed gros- 

 beak^s food. Scale insects were fed upon 

 by all but 81 of the 226 birds examined. 



The destructiveness of these insects need 

 not be explained to anyone in the western 

 fruit-growing region, where the disastrous 

 effects of their presence have been keenly 

 felt for many years, longer in fact than in 

 any other part of the country. Suffice it to 

 say that scale insects cause more trouble and 

 loss to fruit growers than all other pests 

 combined, and the damage from them is to be reckoned by millions of 

 dollars. 



The black-headed grosbeak evinces a distinct preference for the 

 most widely distributed and abundant scale insect on the coast — -the 

 black olive scale (Saissetia olece, fig. 36) the importance of which 

 the following notes from the writings of Prof. 

 E. J. Wickson, of the University of California, 

 will serve to show. It affects both citrus and 

 deciduous trees, but is especially troublesome 

 to the olive, and it will spread quickly to orna- 

 mental plants and vines. It is a very difficult 

 scale to subdue, and in spite of the fact that 

 immense numbers are killed by parasites it is 

 still a grievous pest. This insfeot constitutes 

 20.32 per' cent of the grosbeak's entire fdod, 

 being eaten by 128 birds, many of which had 

 secured from 12 to 32 scales each. If this serv- 

 ice alone is not sufficient to atone for all the 

 bird's depredations on fruit, the latter must be 

 held at an exceedingly high price. 



Moreover, all has not yet been said in the 

 bird's favor. It does not confine itself to the 

 black olive scale alone, but at times probably preys extensively on 

 other species. Sixteen other grosbeaks consumed enough scales to 

 make up 2.26 per cent of the total food. Among the scales they ate 

 are the bro^n apricot scale {Eulecanium armeniacum) and the frosted 

 scale (E. pruinosum) , both of considerable economic importance. 



,f;: 



Fig. 36. — Black olive 



scale (Baissetia oleis) . 

 (From 'Marlatt, Bureau 

 of Entomology.) 



