RED-CLOVER SEED PRODUCTION. 19 
In order to determine the efficiency of the honeybee as a cross- 
pollinator of red clover, a cage 12 feet square and 6 feet high, made 
of galvanized-wire screen having 4 meshes to the lmear inch, was 
erected in the same field as the bumblebee cage. It was previously 
determined that a mesh of this size would permit a honeybee, or any 
insect smaller than a honeybee, to pass through, but would not per- 
mit bumblebees to do so. Two weeks before the clover came into 
bloom a small colony of honeybees was placed in one corner of this 
cage (fig. 6). The bees soon learned to pass through the screen. By 
the time the clover began to bloom the bees had become accustomed 
to the cage, and while most of them worked on flowers outside, some 
could always be seen at work on the clover within the cage. Bees 
Fig. 6.—A screen cage in which a hive of honeybees was placed, in order to determine the efficiency of these 
insects as pollinators of red clover. 
working on the clover within the cage were observed to collect pollen 
from the flowers and carry it to the hive. 
As soon as all the flowers in the cage were mature, an area 4 feet 
square was measured off and all heads within this area were collected, 
kept separate, and thrashed by hand. Of the 623 heads collected 
from this area an average of 37.2 seeds per head was obtained. 
The higher yield of seed obtained in the honeybee cage than in the 
bumblebee cage may be attributed, at least in part, to the larger num- 
ber of bees which had access to this clover. However, the ratio of 
honeybees to bumblebees was no greater in the cages than in the 
clover fields in the vicinity of Ames in 1911. 
In 1911 the precipitation at Ames was 2.48, 3.83, and 0.39 inches 
below normal for June, July, and August, respectively. When the 
