INSECTS IN RELATION TO OTHER ANIMALS 29 1 



chafer was compensated by a general diminution of the ratios 

 of all the other elements, and not by a neglect of one or two 

 alone. If the latter had been the case, the criticism might 

 easily have been made that the birds, in helping to reduce one 

 oscillation, were setting others on foot. 



" 3. The fact that, with the exception of the indigo bird, the 

 species whose records in the orchard were compared with those 

 made elsewhere, had eaten in the former situation as many 

 caterpillars other than canker-worms as usual, simply adding 

 their canker-worm ratios to those of other caterpillars, goes 

 to show that these insects are favorites with a majority of 

 birds." 



The Relations of Birds to Predaceous and Parasitic In- 

 sects. The false assumption is often made that a bird is 

 necessarily inimical to man's interest whenever it destroys a 

 parasitic or a predaceous insect. Weed and Dearborn attack 

 this assumption as follows : 



" Suppose an ichneumon parasite is found in the stomach of 

 a robin or other bird : it may belong to any one of the follow- 

 ing categories : 



" i. The primary parasite of an injurious insect. 



" 2. The secondary parasite of an injurious insect. 



" 3. The primary parasite of an insect feeding on a noxious 

 plant. 



" 4. The secondary parasite of an insect feeding on a nox- 

 ious plant. . 



" 5. The primary parasite of an insect feeding on a wild 

 plant of no economic value. 



" 6. The secondary parasite of an insect feeding on a wild 

 plant of no economic value. 



" 7. The primary parasite of a predaceous insect. 



" 8. The primary parasite of a spider or a spider's egg. 



" This list might easily be extended still farther, and the 

 assumption that the parasite belongs to the first of these cate- 

 gories is unwarranted by the facts and does violence to the 

 probabilities of the case. 



