BLACKHEAD VS. SCALE INSECTS. 73 
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 (Coccide), 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 tr eel eats aanweenl 
any other part of the country. Suffice it to (Pateacrita vernata). (From 
say that scale insects cause more trouble and ¢ EVERY eb dunhowels 
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 olee, 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 insect constitutes 
20.32 per cent of the grosbeak’s entire food, 
being eaten by 123 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 
Fic. 36.— Black olive é é a 
scale (Saissetia olee). held at an exceedingly high price. 
(From Marlatt, Bureau. Moreover, all has not yet been said in the 
am 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 brown apricot scale (Z'ulecanium armeniacum) and the frosted 
scale (E'. pruinosum), both of considerable economic importance. 
