INTRODUCTION". 7 



Farmers and horticulturists have never accused the flycatchers of 

 doing any harm to their crops. The most that has been said against 

 them is that certain of the larger species feed to a harmful extent 

 upon honeybees. Stomach examinations, however, do not sustain 

 this accusation. Honeybees do not form an important percentage of 

 the food, and, moreover, a large proportion of those eaten are drones 

 or males, of which, as is well known, there is in every hive a super- 

 fluity. The real harm, if any, done by this family of birds is in the 

 destruction of predaceous and parasitic Hymenoptera. Of the former, 

 however, so few are eaten that their loss is of no practical importance. 

 Some parasitic Hymenoptera are taken by most flycatchers, and 

 with certain of the smaller species they amount to a considerable 

 percentage of the food. While theoretically this is harmful to the 

 interests of husbandry, the precise amount of the damage is impos- 

 sible of estimation. The parasites themselves often destroy useful 

 insects, including other parasites, or are themselves destroyed by 

 other insects, so that the question of the final result involves a prob- 

 lem so delicate and complicated as to preclude exact solution. 



It is a well-known fact that Hymenoptera, aside from the parasitic 

 species, are largely instrumental in the pollenization of plants, and 

 many species are absolutely dependent upon insects for this service. 

 So completely is this true that where cucumbers are raised under 

 glass it is necessary to keep a hive of bees in each house or the crop 

 will fail. In view of this fact the birds must be considered to render 

 a very questionable service in destroying so many of these insects. 

 On the other hand a single insect can pollinate a great many flowers, 

 and as these insects are usually superabundant the harm done by 

 their destruction is less than might at first be supposed. Moreover, 

 this order of insect is not the only one that enjoys the distinction of 

 serving as pollen bearers. Many beetles and flower-loving flies also 

 transfer pollen from flower to flower and so help in this necessary 

 work. 



In considering the economic bearings of the food of the flycatchers 

 one is impressed by the fact that it includes a large percentage of use- 

 ful insects. The great order of Hymenoptera, which constitutes one- 

 third of the average food of the flycatcher family, may fairly be 

 classed as beneficial. The absolutely harmful species in this group 

 are comparatively few, while the decidedly useful ones are many. As 

 shown in the following pages, however, their food includes many 

 insects other than Hymenoptera which are seriously destructive to 

 crops, and it is believed that, weighing as impartially as possible the 

 injuries done and the benefits conferred by them, their good qualities 

 outweigh the bad and that the flycatchers herein discussed fairly earn 

 the right to live unmolested. 



