BIRDS IN RELATION TO THE ALFALFA WEEVIL. 3 



In the Salt Lake Valley the bulk of the larvae appear in May and 

 June, but at higher altitudes somewhat later. The period of greatest 

 abundance is at the time of the first alfalfa harvest. The insects 

 usually make heavy inroads on the first crop and after the harvest 

 do serious harm by retarding the growth of the second crop. All 

 new shoots are devoured as soon as they appear, and a field frequently 

 remains barren for three to five weeks after the first cutting. 



When full-grown the larvae cease feeding, drop to the ground, and 

 spin rather loosely woven cocoons, which are often attached to dry 

 vegetation at the base of the plant. The insect now passes through 

 the pupal stage and in from one to two weeks emerges as the adult. 

 In this stage it is covered with many fine scales or hairs which give it 

 a light brown color. The adults begin to appear in large numbers 

 about the first of July and may often be found clustering by hun- 

 dreds upon vegetation about the borders of recently cut fields or 

 near the bases of newly constructed haystacks. Frequently they feed 

 upon the foliage and scar the stems of plants other than the Le- 

 guminosse; the writer has seen healthy amaranth plants laid pros- 

 trate in a comparatively few hours. 



After a short period of flight, when again some may fall prey to 

 birds that feed on the wing, the insects seek hidden places for the 

 winter's hibernation. Beginning soon after early August the weevils 

 appear less in evidence. 



DISTRIBUTION OF WEEVIL-EATING BIRDS IN THE TERRITORY 

 COVERED BY FIELD WORK. 



The following somewhat general synopsis of the distribution and 

 relative abundance in Utah of native birds will give a fair idea of 

 the species most available as aids in the fight against the alfalfa 

 weevil. This, combined with details regarding each species, as later 

 presented, will show which birds are doing the most good in any 

 locality. 



One of the regions most severely infested by the weevil was that 

 immediately south and southwest of Salt Lake City, extending east 

 and west to the edge of the irrigated land. This has an average 

 width of 4 miles and through it flows the Jordan River. In 

 this area the English sparrow is the most abundant bird. Next 

 comes Brewer's blackbird and in smaller numbers are the red- 

 winged blackbirds, which confine the bulk of their feeding to the 

 vicinity of marshes along the river or places where lack of drainage 

 has produced ponds. Following these are Brewer's, vesper, and lark 

 sparrows, and meadowlarks. Robins, though very numerous in 

 migration, are not so frequently met at a later date. The remaining 

 common birds, named approximately in the order of their abundance, 



