24 



NORMAL AND EXPERIMENTAL POLLINATION. 



Landing-platform removed. — The landing-platform in this flower 

 consists of the lower two sepals. When these were removed, juxtus hovered 

 above two flowers without landing. At the third flower it landed success- 

 fully by placing the hind pair of legs on the sepals of an adjoining flower. 



A comparison was made between 25 normal and 25 mutilated flowers, 

 consisting of 5 of each type. In the fifth type of mutilation, pieces of grass 

 culms 2 cm. long were used to close the nectary openings and to change the 

 appearance of the flowers (table 5). 



Table 5. — Visitors to normal and mutilated flowers. 



The mutilated flowers were visited somewhat more frequently than the 

 normal ones, the kind of mutilation making little difference, except when 

 the grass section was present. However, the two species exhibited a marked 

 difference in behavior, Bombus edwardsi visiting twice as many mutilated 

 flowers as normal ones and juxtus but half as many. In the case of the 

 grass section, two individuals of each species of Bombus tried hard to push 

 the ligule into the nectary, but did not succeed, their persistent efforts at 

 the proper spot indicating that they knew where the nectary was. 



ARTIFICIAL AND PAINTED FLOWERS. 

 Crepe-paper corollas. — In order to give Delphinium the same general 

 form as Rubus deliciosus, disk-like corollas of red, white, green, yellow, 

 or blue paper were placed around the pedicels after the floral envelopes 

 had been removed. This did not change the odor or the essential parts of 

 the flower, but increased the size in addition to changing the color. There 

 were 147 open flowers under observation, 10 of each of the 5 colors, and 97 

 normal ones, approximately twice as many normal as changed flowers. 

 During the hour and a half of observation, Bombus juxtus was the only 

 visitor, going to 93 normal flowers and to one with a green paper corolla. 

 During this time it visited 4 normal flowers on one branch where the majority 

 were blue, and 5 normal ones on a branch where most of them were white, 

 but in neither case did it venture to try the artificial flowers. 



Crepe-paper corollas with spurs. — In order to study the response to 

 color without change of form, life-like crepe corollas with spurs were used 

 to replace the floral envelopes. In addition to 27 normal flowers, 4 of each 

 of the five colors, red, blue, green, yellow, and white, were used for com- 

 parison, with the following results. Three individuals of Bombus juxtus 

 visited 3, 2, and 3 normal flowers respectively, not even stopping to inves- 

 tigate those with crepe corollas. Two B. proximus visited 2 normal flowers 

 each and no crepe ones. This group of flowers was covered over night with 



