CONTROL OF INSECT PESTS McATEE 427 



typical Utah farm was about 500,000. To this must be added the 

 number eaten by the adult sparrows, which made of them about a 

 fifth of their food. Most of the common birds of northeastern Utah 

 were depending upon alfalfa weevils for almost a sixth of their 

 entire food, and the destruction of these pests by this warfare is 

 almost beyond conception. 



The good work of birds in preying upon another weevil pest, the 

 cotton boll weevil, must not be overlooked. Sixty-six kinds of birds 

 are known to feed upon this formidable cotton destroyer, probably 

 the most effective being the orioles, which actually remove the boll 

 weevils from the place where damage begins — that is, the squares, or 

 flower buds, of the cotton plants — and the swallows, which feed upon 

 the weevils when in flight and extending their range. No fewer than 

 41 boll weevils were found in a single stomach of the Bullock oriole, 

 and large numbers are habitually taken by all species of swallows; 

 every one of a series of 35 eaves swallows had eaten them, the largest 

 number in any stomach being 48, and the average 19. 



All the students of bark beetles (Scolytidce) have been impressed 

 with the usefulness of woodpeckers as enemies of these pests, and 

 there are at hand six different statements indicating their control 

 value from the pens of Dr. A. D. Hopkins, Mr. J. L. Webb, Dr. 

 M. W. Blackman, and Dr. J. M. Swaine. We will quote only one of 

 these, and that from Dr. Hopkins. He says with regard to the 

 spruce-destroying bark beetle which has been responsible for the loss 

 of many billions of feet of timber in the Northeastern States : 



The principal enemy of tlie spruce-destroying beetle, and other bark-infest- 

 ing enemies of the spruce, consists of the woodpeckers, which destroy, it is 

 believed, from 50 to 75 per cent of the broods of the spruce beetle in many 

 hundreds of trees each year." 



FLIES (DIPTERA) 



Only a single instance of control by birds of a dipterous pest has 

 come to notice, and that is one in which artificial use was made of 

 the birds. Dr. Samuel G. Dixon, late health commissioner of Penn- 

 sylvania, writes: 



After trying the ability of fish to devour larvae and pupne of mosquitoes 

 with varied success, I built two dams near together on the same stream, 

 so that each would have the same environment for the breeding of mos- 

 quitoes. Each covered nearly 1,400 square feet. In one 20 mallard ducks, 

 Anas platyrhyncha, were permitted to feed, while the other was entirely pro- 

 tected from waterfowl, but well stocked with goldfish, Carassius auratus 

 variety americanus. 



The one in which the ducks fed was for several months entirely free from 

 mosquitoes, while the pond protected from ducks and stocked with fish was 

 swarming with young insects in different cycles of life. 



"Bull. 28, U. S. Bur. Ent, 1901, p. 48. 



