INSECTS IN RELATION TO OTHER ANIMALS 241 



II 



beetles eaten; in the second half of the month the food consists chiefly 

 of small fruits, especially raspberries, cherries and currants; so that for 

 the month as a whole, only forty-nine per cent, of the food is made up 

 of insects. This falls to eighteen per cent, in July, when three quarters 

 of the food consists of small fruits, mostly blackberries, however. In 

 August, with the diminution of the smaller cultivated fruits, the per- 

 centage of insects rises to forty-six per cent., nearly one half of which is 

 made up of ants and the rest of caterpillars, grasshoppers, Hemiptera, 

 Coleoptera, etc. In September, with the appearance of wild cherries, 

 elderberries, Virginia creeper berries and grapes, these are eaten to the 

 extent of seventy-six per cent., the insect element of the food falling to 

 twenty-one per cent., of which almost half consists of ants, and the 

 remainder of beetles and a few caterpillars. 



For the entire year, as appears from the study of seventy specimens 

 by Forbes, insects form forty-three per cent, of the food of the catbird 

 and fruits fifty- two per cent. As the injurious insects killed are offset 

 by the beneficial ones destroyed, " the injury done in the fruit-garden by 

 these birds remains without compensation unless we shall find it in the 

 food of the young," says Professor Forbes. And this has been found, to 

 the credit of the catbird; for Weed learned that the food of three nest- 

 lings consisted of insects, sixty-two per cent, of which were cutworms 

 and four per cent, grasshoppers; while Judd found that fourteen nest- 

 lings had eaten but four per cent, of fruit, the diet being chiefly ants, 

 beetles, caterpillars, spiders and grasshoppers. In fact, Weed believes 

 that, on the whole, the benefit received from the catbird is much greater 

 than the harm done, and that its destruction should never be permitted 

 except when necessary in order to save precious crops. 



Bluebird. The excellent reputation which the bluebird bears every- 

 where as an enemy of noxious insects is well deserved. From a study of 

 one hundred and eight Illinois specimens, Forbes finds that seventy- 

 eight per cent, of the food for the year consists of insects, eight per cent, 

 of Arachnida, one per cent, of Julidae and only thirteen per cent, of 

 vegetable matter, edible fruits forming merely one per cent, of the entire 

 food. The insects eaten are mostly caterpillars (chiefly cutworms), 

 Orthoptera (grasshoppers and crickets) and Coleoptera (Carabidae and 

 Scarabaeidae) . Though some of the insects are more or less beneficial to 

 man, such as Carabidae and Ichneumonidae (respectively predaceous and 

 parasitic), the beneficial elements form only twenty-two per cent, of the 

 food for the year, as against forty-nine per cent, of injurious elements, the 

 remaining twenty- nine per cent, consisting of neutral elements. The food 



16 



