2 BULLETIN 104:, U. S. DEPABTMENT OF AGRICULTURE. 



unobserved access of minute pollen-bearing insects. None of the 

 common visiting insects other than thrips is minute enough to 

 gain entrance through the interstices between the mouth of the 

 paper bag and the stem when the bag is tied closely about the beet 

 spike. Thrips, however, are so tiny as scarcely to be visible to the 

 naked eye, the mature larvae being about -^j inch long and only 

 about ^ inch long immediately after hatching; hence it seemed 

 probable that some of these insects might have crawled up within 

 the mouth of the tied bags and dropped on the stigmata of the 

 isolated flowers some of the pollen they were carrying. 



OCCURRENCE OF THRIPS ON BEET FLOWERS. 



Besides several other species not identified, the Bureau of Ento- 

 mology determined the following among specimens of thrips col- 



Fig. 1.— The bean thrips (Heliothrips fasciatus): a, Adult female; 6, ventral side of abdominal segment of 

 same; c, antenna of same, a, Greatly enlarged; 6, c, more enlarged. (After Russell.) 



lected from beet flowers at Garland, Utah, hi 1909 and 1910: Helio- 

 thrips fasciatus L. (fig. 1), Frankliniella fusca Hinds, and Frank- 

 liniella tritici Fitch. The species most abundant during the seasons 

 of 1911 and 1912 at Ogden, Utah, was Thrips talari, the onion thrips. 

 The few observed at Jerome, Idaho, during the summer of 1913 have 

 not yet been determined. 



At Garland the seed beets were grown near fields of alfalfa, whence 

 many of the thrips found on beets doubtless migrated, the same species 



