76 NORMAL AND EXPERIMENTAL POLLINATION. 



exposed to view. As the bee sucks nectar, the hairs of the thorax are 

 brushed against the anthers or the stigma. 



Petals split to the base. — Osmia phaceliae usually stands on the lower 

 lip, and a single petal suffices to support it when the lobes are split. 0. 

 bruneri, on the contrary, is so heavy that a single petal will not support its 

 weight, and hence it was unable to obtain a foothold. Bombus juxtus 

 had even greater difficulty in landing because of its weight. It finally 

 found a position in which it was supported by the two outer petals. It 

 then felt around with its ligule until it found the arch under the stamens and 

 went to the nectar in the usual manner. Vespa germanica entered these 

 flowers, but stayed only a very short time, acting as though uneasy because 

 of the unsteady foothold. 



PENTSTEMON GLAUCUS. 

 NORMAL POLLINATION. 

 Normal behavior. — Thanaos martialis lands on the lower lip of the 

 corolla, where it feels around with its ligule until it finds the nectar, the 

 anthers and stigma rubbing against the hairs of its back meanwhile. 

 Bombus proximus and edwardsi enter the flowers by landing on the lower 

 lip and going directly to the nectary. One bee tried to turn around and 

 enter a half-open bud upside down, but was not successful. Osmia pent- 

 stemonis works on the anthers upside down, so that the ventral scopa rubs 

 them. It comes out of the normal flower head first and, as it starts to fly, 

 the back of its head comes in contact with the anthers or stigma tip. 



EXPERIMENTS. 



MUTILATED. 



Upper lobes split to base. — Osmia pentstemonis, after trying to land 

 on the projecting staminode, placed its front legs on the outer lobes of the 

 lower lip and the others on the middle lobe and worked easily, reaching 

 the nectar readily. The corolla mouth is so large that the bee does not 

 usually come in contact with the anthers and the stigma. Its scopa rubs 

 the hairs of the staminode, but pollination is not often effected by this 

 visitor. Bombus morrisoni landed on some of the flowers, but flew away 

 at once, while in other cases it inspected them without landing. 



Lower lip removed. — Osmia pentstemonis had difficulty in landing, 

 slipping back and forth and its head rubbing the anthers. 



Outer lobes of lower lip removed. — Thanaos martialis normally 

 places the front pair of legs on the outer lobes and the weight of its body on 

 the middle one. With the outer lobes removed it finally succeeded in landing 

 by putting its front legs at the edges of the middle lobe and the weight of its 

 body on a bud under the flower. 



Staminode removed. — Bombus juxtus landed, then moved from side 

 to side, and backed out. It started into the flower again, stopped, and 

 went directly to the nectar. In normal flowers it follows the staminode to 

 the nectar at once. 



