SWALLOWS. 29 



been informed, bee keepers do not regard the destruction of drones as 

 injurious to the swarm. In most cases drones are superabundant 

 and instead of contributing to the food supply they are a drain upon 

 it, so that the destruction of some of the surplus males is a positive 

 benefit to the colony. 



Hemiptera, or bugs, stand next to Hymenoptera in importance in 

 the food of the cliff swallow. They form a little less than r27 percent 

 of the whole diet, and are represented by eight families, namely, 

 assassin-bugs, leaf-bugs, squash-bug family, stink-bugs, sliield-bugs, 

 tree-hoppers, leaf -hoppers, and jumping plant-lice.'* All of these, 

 excepting the assassin-bugs, are injurious to plants, and some of them 

 are pests al all times. Of these, probably the leaf -hoppers ( Jassidse) 

 are the worst. They suck the juices of plants, particularly grasses, 

 which they infest by millions. They are said to have but few enemies, 

 of which birds are the most effective. It is probable that they are 

 captured by swallows when just skimming over the surface of fields, 

 or are snatched from the tops of grass and weeds. They were found 

 in 27 stomachs. 



Leaf -bugs (Capsida?) are a very large family of harmful insects, 

 which feed Almost entirely upon plants. Some species of this family 

 are pests of the worst description. Leaf-bugs were contained in 43 

 stomachs. The other insects of this order are more or less harmful, 

 but were not eaten so extensively. 



Beetles of all kinds aggregate a little less than 19 percent. Of 

 these, 2 i^ercent were useful species, such as carabids and coccinellids. 

 The others belong to 12 different families, most of which are harmful, 

 some very mucli so. Among them were a number of aquatic species. 

 These were probably captured by the swallows when flying just above 

 the surface of the water. The principal flights of beetles do not 

 occur during the day, but chiefly in early evening and at night. 



Flies are eaten by cliff swallows to the extent of nearly 12 percent 

 of the food. Most of these are the species commonly known as 

 gnats, but one stomach contained a large horsefly (Tabanida?). The 

 gnats have a habit of swarming afternoons and evenings, when many 

 are probably snapped up by swallows. 



The i^mains of dragon-flies, lace-winged flies, ephemerids. and 

 spiders make up the rest of the food, or a little more than 3 percent. 

 As spiders do not fly, it may be asked how they were captured by 

 the swallows. They probably were snatched from their webs or from 

 the tops of weeds as the birds passed. Swallows pick up substances 

 even from the ground, as is shown by the vegetable component of 

 their food, and by other facts to be given presently. 



n riant-lice and scale-insects were not present, ami this may be explained from 

 the fact that their lives are passed mostly in a wingless condition. 



