40 BULLETIN 107, U. S. DEPARTMENT OF AGRICULTURE. 



bers is of the utmost importance in suppressing the number of the 

 season's brood. Though the cliff swallow does not arrive in Utah in 

 abundant numbers much before the 10th of May many breeding 

 alfalfa weevils may still fall as its prey. These birds feed on no 

 product of the farm unless it is an occasional honey bee, but they 

 include in their diet many of our most serious insect pests, note- 

 worthy among which is the cotton-boll weevil in the Southern States. 



BANK SWALLOW. 



(Riparia riparia.) 



The finding of two adult weevils in the stomach of a single bank 

 swallow is the only evidence that this bird is among the enemies of 

 the insect. Other elements in the food were numerous dung beetles 

 (Aphodius) and several flies, including a syrphid. 



ROUGH-WINGED SWALLOW. 



(Stelgldopteryw serripentvis.) 



Over much of the alfalfa district of Utah the rough-winged is 

 the most abundant of swallows. Nesting in banks of streams or 

 railway cuts, they at times are in close proximity to infested fields. 



Examination of twenty-one of these birds revealed the fact that 

 the greatest consumption of weevils took place late in summer, when 

 the year's brood had taken wing. 



Of five birds collected in May, two had fed on the insect, which com- 

 prised 4 and 2 per cent, respectively, of their food. The remains 

 of flies, some of which were of the genus Bibio (March flies) , formed 

 nearly two-thirds of the stomach contents, while small Hymenoptera 

 and dung beetles {Aphodius) also figured prominently in the per- 

 centages. 



During June only three of a series of eight had fed on the weevil, 

 to an average extent of 1 per cent of the stomach contents for the 

 month. Flies of various kinds were taken in considerable numbers 

 and formed about three-fourths of the food. Small Hymenoptera 

 were present in six of the stomachs. 



In July the birds began to prey upon the flying adults of the year's 

 brood. Six of the eight swallows examined had fed on the insect, 

 which composed 23 per cent of their food. The weevils had been 

 taken on the average of nearly 8 per bird, 18 being the highest num- 

 ber recorded from a single stomach. In this case it formed over 

 a third of the contents, and in another 11 weevils made up nearly a 

 half. Ants, found in each of the stomachs, amounted to over half of 

 the swallow's food. Neuropterous insects were also detected in 

 several cases. 



