ALFALFA SEED PRODUCTION. 15 
MISCELLANEOUS INSECTS. 
A number of species of small insects visit alfalfa flowers, not for the 
purpose of getting honey, but to feed upon the pollen and the cellular 
tissue of the flower. The most common insects of this kind are the 
thrips. These insects are found in all parts of the United States, and 
have frequently been abundant in the alfalfa flowers at Arlington 
farm, Virginia; Chico, Cal.; Pullman, Wash.; and at Chinook and 
Havre, Mont. At Pullman 1,119 thrips were found on 16 racemes 
of alfalfa flowers, or an average of 69.9 thrips on the flowers of each 
raceme. At Havre 48 thrips were found on 13 racemes. These 
minute insects do not trip the alfalfa flowers. 
_ In conducting the various experiments described in this paper, 
it has been observed that even when the thrips are present in very 
large numbers the flowers very rarely develop into pods and seed 
unless tripped. On the other hand, when the flowers are tripped, a 
large proportion usually produce pods and seeds, even though the 
thrips are very abundant. The evidence at hand indicates that 
the thrips are neither appreciably beneficial nor injurious in their 
influence upon the development of alfalfa seed. | 
Another insect commonly found on alfalfa flowers is the tarnished 
plant bug (Lygus pratensis). Blister beetles (E'picauta puncticollis 
Mannerheim) are found on alfalfa in abundance at Pullman, Wash., 
feeding on the more tender portions, especially the stamens and style. 
At Brookings, S. Dak., occurs the related Macrobasis unicolor Kirby. 
This beetle, according to R. A. Oakley, does considerable damage 
to the flowers, but incidentally trips many. 
EFFECTS ON SEED SETTING OF VISITS OF INSECTS WITHOUT TRIPPING FLOWERS. 
To determine whether or not the visiting of flowers by insects 
without actual tripping aids in seed setting, observations were made 
at Chico, Cal., as shown in Table VII. The plants designated as A, 
B, and C were in full bloom at the time of beginning the experiment, 
and up to that time were not protected in any way. After counting 
and tageing the old and young flowers to be observed, the plants 
were screened with tarlatan netting, witk the exception of a portion 
of plant B, which was left to develop under natural conditions. 
_ The flowers designated as old flowers were the oldest on the plant 
not tripped at the time the experiment was started, and many of 
them probably had been visited one or more times by bees or other 
insects without tripping. That insects had visited the older flowers 
is merely assumption, but as many bees and other insects were work- 
ing the alfalfa flowers on the days immediately preceding the starting 
of the experiment, this seems probable. The flowers designated as 
young flowers were not yet in bloom when they were screened. 
