2 BULLETIN 104, U. S. DEPARTMENT 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 -^ inch long and only 
about 7V 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 fxsciatus): a, Adult female; b, 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, in 1909 and 1910: Helio- 
tJirips 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 tabaci, 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 
