76 BIRDS OF CALIFORNIA AFFECTING FRUIT INDUSTRY. 



food contained in a bird ; s stomach at a given time is only a fraction 

 of the daily consumption, we may infer that not many days pass in 

 the life of a bush tit when it does not eat a considerable number of 

 scales. 



Before leaving the subject it may be well to add a few words on 

 the economic relations of scale-insects in order that the value of the 

 work done by the bush tit may be fully appreciated. Mr. Marlatt 

 says: 



The most destructive insect enemies of fruits in California are undoubtedly 

 the scale insects, few if any other insects, aside from the grape Phylloxera, at 

 all approaching them in this respect. Of these, the ones of greatest moment 

 and in the control of which vast sums of money are expended are the black 

 scale, the red scale, and the San Jose scale. For the olive and citrus plants 

 the black scale is the most important, and for the deciduous plants the San 

 Jose scale takes similar rank.a 



When the immense number of bush tits and other birds in Califor- 

 nia that eat scale insects is considered, it becomes evident that the 

 aggregate of these pests annually destroyed by them must be enor- 

 mous. It may be urged that despite the attacks of birds, scales have 

 caused, and still are causing, much damage to fruit trees, and that the 

 work of birds alone is inadequate to save the trees from destruction. 

 This is undoubtedly true, but it must be remembered that the birds 

 are confronted with abnormal conditions. The great and rapid 

 development of the fruit-growing industry on the Pacific coast and 

 the simultaneous and widespread introduction of several new species 

 of scales resulted in a sudden increase of these pests, while their ene- 

 mies, the birds, enjoyed no such opportunities for increase. In time, 

 no doubt, an equilibrium would have been reached, and birds would 

 have played an important part in establishing this by exerting a con- 

 stant and steady check upon the increase of scales. Unaided, how- 

 ever, their numbers are too few to cope with the insects which, under 

 favorable conditions of climate and environment and unmolested by 

 other natural insect enemies, multiply to countless myriads. 



The remaining portion of the hemipterous food of the bush tit. 

 over 31 per cent, is made up of plant-lice, tree-hoppers (Membracidse), 

 leaf-hoppers (Jassidse), some jumping plant-lice (Psyllidse), and a 

 considerable number of false chinch bugs (Nysius angustatus) , with 

 a few lace-bugs (Tingitidae). Of the plant-lice little need be said. 

 As pests to vegetation their reputation is world-wide. No part of a 

 plant is free from attack. They infest leaves, trunk, and roots, and 

 some of their legions of species prey upon nearly every kind of land 

 plant. They are a frequent element of the food of the tit, but as their 



« Insect control in California, by C. L. Marlatt, U. S. Dept. of Agriculture, 

 Yearbook, 1896, p. 220. 



