BULLETIN 104, U. S. DEPARTMENT OF AGRICULTURE. 
other plants, but more especially through breeding. Eggs are 
deposited and hatched on the spikes themselves. On hatching, the 
young larvae quickly seek the flowers, doubtless attracted by the 
pungent fragrance of the nectar, and literally wallow in the nectar 
and pollen, avidly drinking the one and voraciously devouring the 
other. 
Observations covering five seasons have shown that several species 
of Thysanoptera visit beet flowers and that the number of individuals 
varies greatly with the locality and general environments, notably 
with the crops in the vicinity. At Jerome, Idaho, in 1913, on land only 
recently cleared from sagebrush, thrips were rather scarce, although 
somewhat abundant in alfalfa in near-by 
fields. These insects have also been seen in 
moderate abundance on seed beets in Indiana 
and Michigan. 
THRIPS AS POLLEN BEARERS. 
The writer has been able to discover in the 
literature very little reference to thrips as a 
pollen bearer and no proof of its ability to 
bring about the fertilization of flowers. 
Darwin was familiar with the visits of thrips 
and kept in mind the possibility that they 
might gain entrance through his nets. 
Hermann Muller * records their occurrence 
in the flowers of several genera and species, 
but does not mention beets. In a paragraph 
on Thysanoptera he says that " probably few 
flowers, if any, are altogether exempt from 
their visits, and though they have seldom been 
detected in the conveyance of pollen, yet from 
their great abundance, their value as fertilizers 
must not be overlooked. It is almost im- 
possible to exclude these tiny insects by means of nets. The Thysan- 
optera seek both pollen and honey. They seize a single pollen grain 
in their mandibles and convey it to the mouth." 
Uzel, 2 in Bohemia, has noted the visits of several species of Thy- 
sanoptera among sugar and stock beets, but adduces no evidence in 
proof of the actual pollination of those flowers by thrips. 
On August 3, 1911, at the experimental plats in Ogden, Utah, 
spikes of beet flowers were exposed to the fumes of chloroform to 
i Muller, Hermann. The fertilisation of flowers. Tr. and ed. by D'Arcy W. Thompson, London, 1883, 
p. 44-45. 
2 Uzel, Heinrich. tiber die Insekten, welche die Bliiten der Zucker- und Futterriibe besuchen. Zeit- 
schriftfur Zuckerindustrie in Bohmen, Jahrg. 37, p. 182-197, 1913. 
Fig. 3. — Larva of Thrips tabaci 
(second stage) taken from a 
sugar-beet flower. The insect 
carries numerous beet-pollen 
grains on its body. X 50. 
(Sketch of the larva after Rus- 
sell.) 
