^^ 



;. ~ 



ACONITUM COLUMBIANUM. 17 



proceeded exactly as in the first inverted flower, apparently noticing the 

 change of position before landing. One B. bifarius mastered the situation 

 readily and went to five inverted flowers in succession, turning upside 

 down just after alighting at each one. Another B. juxtus landed three 

 times at a group of inverted flowers, tried to push its proboscis into the 

 hood without turning upside down, and in each case failed to find the 

 nectary. 



MUTILATION. 

 Cotton plugs. — When absorbent cotton was placed in the nectary, 

 Bombus juxtus landed, pushed out its proboscis to find the opening, and tried 

 repeatedly to make a way through the cotton into the nectary. At the 

 next flower it hovered but did not land. When the styles and stamens were 

 hidden by a cotton wad, B. bifarius made the same unsuccessful effort to 

 find the nectary opening. Another individual jerked back as it was about 

 to land, and then quickly flew away to the next flower. A third hovered 

 above the flower and departed without landing, as did several others of 

 both species. 



Stamens removed. — Bombus juxtus noticed the change as readily as 

 when the flowers were covered with cotton wads, while B. bifarius either 

 hovered above the flower before alighting, or landed directly and flew away 

 at once without projecting the ligule or trying to find the nectar. 



Hood split. — The hood was split longitudinally in some flowers, thus 

 making them more conspicuous, as it then exhibited a pair of wings ascending 

 behind the nectaries. In some cases this change had no effect upon landing, 

 as it appeared neither to frighten the bees nor to attract them in increased 

 numbers, but in others it greatly increased the attraction. They landed 

 in tHe usual manner, but had a very hard time hanging on to the stamens. 

 Because they were unable to find a suitable position, they often went away 

 without getting nectar. 



Hood removed. — The hood was removed, leaving the two nectaries to 

 project above the remaining flower-parts. This made the nectaries con- 

 spicuous and changed the general aspect of the flower very much. The 

 effect on the visiting bees was not uniform. Bombus juxtus sometimes 

 hovered above the flowers, but did not land, or stopped without pushing 

 out its ligule. Some exposed the ligule, then noticed the change, and flew 

 away. Others were more persistent, for they landed, at once found the 

 slit down which the nectar runs, and emptied each of the nectaries, repeating 

 this performance at the next flower. 



Hood and nectaries removed. — An individual of Bombus juxtus 

 alighted as usual, and explored in all directions with its tongue, in the 

 unsuccessful endeavor to find the opening. One adventurous individual 

 crawled between the side petals as if expecting to find the nectary. When 

 it got through, it turned around, crawled over the stamens, and flew away. 



Lower sepals removed. — Since this is the part of the flower on which 

 Bombus usually rests its hind legs, it found difficulty in balancing properly 

 while seeking the nectary, but finally succeeded in reaching the nectar. 



