NOTES ON POLLINATION OF RED CLOVER 
;59 
three treatments with the brushes while the plots in Table IX 
received but one treatment. 
It will not be necessary to describe the method of pollination 
since this has been done in several papers by Hermann Mueller, 
L. H. Pammel and Charlotte M. King, Roberts 15 and others. 
We might note in this connection that any insect with sufficient 
weight to press down the keel of red clover can pollinate it. 
For this reason various butterflies observed on red clover like 
the large monarch butterfly ( Danais ar chippies) , the cabbage 
butterfly ( Pieris rapae and P. Brassipae) , the yellow butterfly 
( Coleus philodice and C. eurytheme) as well as certain Noe- 
tuidas which are especially common in September, are not nor- 
mal pollinators. Certain Coleoptera also visit red clover but 
they are not normal pollinators though they sometimes no doubt 
transfer pollen from, other plants. The normal pollinators are 
bumble bees, of which we have observed the following at Ames : 
The Bombus pennsylv miens, B. fervidus, B. americanus ; and 
the honey bee Apis mellifica. The bumble bees are generally 
not common on the first crop. In 1915 we observed two bumble 
bees over an area sixteen by sixteen feet in ten minutes on a 
partly cloudy afternoon. 
In order to determine the length of the corolla tubes under 
the most favorable weather conditions we had H. L. Rothschild 
measure the corolla tubes of 1,000 corollas of first crop clover 
and J. H. Frazier measured the corolla, tubes of second crop 
clover. The conditions for the development of red clover flow- 
ers were most favorable this year (1915). Rothschild found 
the average length of first crop to be 9.52 mm. and Frazier 
found the corolla tubes of 500 second crop to have an average 
length of 9.42 mm. The Rothschild measurements were made 
between June 27 and July 6 and the Frazier measurements be- 
tween July 10 and 15. For the purpose of obtaining an aver- 
age the length of ten flowers of each head was measured. 
