20 



NORMAL AND EXPERIMENTAL POLLINATION. 



To render the natural flowers more conspicuous, strips of crepe-paper 

 were cut a half-inch wide lengthwise of the roll. Fine wire was run through 

 this strip along one edge, making a ruffled disk which was placed around 

 the stamens and nectaries. An equal number of normal flowers and of 

 those with red, green, white, yellow, or blue crepe ruffles were used. The 

 flowers appeared very showy and the nectaries and stamens were con- 

 spicuous. Bombus juxtus visited only normal flowers to a total of 29, 

 while bifarius stopped at but 5 normal ones. It hovered low over green, 

 white, and blue modifications, but did not land on them. 



Painted flowers. — In further experiments, flowers were treated with 

 water-colors. The white flowers were usually painted, as they took the 

 colors better than the purple. The perianths were washed on the outside 

 alone. Ten natural flowers and 5 of each color were used, making a total 

 of 30 colored ones, or 3 times as many painted as normal (plate 1). 



Table 4.- 



-Visits of Bombus juxtus to painted fl 



While this species visited nearly twice as many painted as normal 

 corollas, the actual ratio was 39 : 66, indicating a distinct preference for the 

 natural flowers. Among the painted ones, blue, vermilion, and indigo were 

 sought most, green, and yellow less, and red by far the least. 



The response to the colored flowers varied at different times, but the 

 general behavior of visitors is shown by the following field calendar, derived 

 from another experiment: 



9 h 22 m Bombus juxtus at a blue flower as if 

 noting no difference, but passed 

 by flowers painted yellow, red, 

 and green; bifarius passed by all 

 the painted flowers, but hovered 

 as if inspecting them. 



9 35 Bifarius passed over the painted 

 flowers, but flew slowly as it 

 looked them over. 



9 45 Juxtus, purple, orange-red. 



9 50 Juxtus took nectar, then hovered above 

 red and then purple flowers. 



9 55 Juxtus, green, and then flew past a 

 brown and a green one, after 

 hovering above each for a short 

 time. 



ll h 15 n 

 11 17 

 11 20 

 11 21 

 11 23 

 11 24 

 11 26 

 11 27 

 11 35 



11 37 

 11 39 



Juxtus, green. 



Juxtus, orange-red for 45 seconds. 



Bifarius, red, red. 



Juxtus, blue, purple. 



Juxtus, yellow. 



Juxtus, blue. 



Juxtus, blue. 



Juxtus, blue, purple. 



Bifarius, purple, orange, red, purple, 



blue, purple; passed over brown 



and yellow. 

 Juxtus, yellow. 

 Juxtus, purple, blue; passed by yellow, 



red, and green. 

 Bifarius, purple, blue, green, purple, 



red, white. 



During the time of the above observations, Bombus visited normal 

 flowers as well as the colored ones listed. A summary shows that the bees 

 visited flowers of all colors used except brown. Of the 32 visits recorded, 



