8 Campbell, Insectivorous Birds. S^^ "j"iy 



fruit and grain crops. During other seasons, however, they make 

 ample compensation by keeping down small reptiles, injurious 

 insects, and weeds. 



The carnivorous section, including all the much- abused Hawks, 

 are undoubtedly of great importance, for they check not only small 

 grass-eating birds (Quail and Finches) but small animals and 

 reptiles, as well as some of the larger insects. If they do take 

 occasional chickens from the poultry-yard, may they not be well 

 forgiven ? 



Turn for awhile to the other aspect of bird-life, and examine the 

 forms that the insectivorous birds are designed to hold in check. 

 Here there is found a complicated matter. The insect inhabitants 

 of the land, especially the portions most opened, are not in the 

 main the original species. Add to this the alarming fact that 

 surviving native species have frequently been driven to seek food 

 on introduced plants because of the clearing away of their own 

 natural forests, and we have a state of affairs that calls for careful 

 thought and treatment. 



The insects the producer has now to face can be grouped under 

 four heads — 



A. Insects brought on introduced plants (indigenous to the 

 plants in their respective native countries) — instance, the codlin 

 moth. When a form is brought to a new area, free from its parasites, 

 it increases alarmingly, unless some other parasite rises up to carry 

 on the work of keeping it in check. 



B. Insects native to a plant, but which enlarge their tastes when 

 taken abroad. Many scale-insects might be cited under this head. 

 Though the food of many of these is restricted to a particular 

 genera, or even species, of plant, there are others which spread 

 from one class of food to another. 



C. Insects native or aboriginal to a country attacking introduced 

 plants. When the land was cleared and planted with fruit trees 

 native root-borers were tempted, when food supply gave out, to try 

 the nearest living tree. In a short time they altered their habits 

 to suit their new surroundings. Many Australian insects have so 

 taken up with introduced plants that they now seem part and 

 parcel of them. Besides root-borers, the native wattles and gum 

 trees have given trunk-borers to the peach, cherry, plum, and elm 

 trees, as well as the cottony cushion scale and the black scale to 

 citrus trees, while the little sweet-rooted creeper (Glycine) has given 

 a most destructive caterpillar to the European vine and the 

 American Virginia creeper. In the case of the cushion scale, this 

 was only a preliminary to its spread among the citrus groves of 

 California and Florida, where it was only after many years that 

 the happy thought of introducing some of its parasite ladybird 

 beetles from Australia put a stop to its devastations. 



Lastly, I). Native omnivorous insects. The original vegetation 

 having been cleared from the land, native omnivorous insects like 

 the grasshojiper, locust, c-(teri)illar, and chafer naturally turned 

 for their food supply to introduced plants, and it is to this class 



