RUBUS DELICIOSUS. 



29 



EXPERIMENTS. 



MUTILATION. 



Petals split or shortened. — When each petal was cut lengthwise into 

 four ribbons, giving a daisy-like appearance to the flowers, Bombus juxtus, 

 B. morrisoni, and Andrena vicina visited them just as they did normal 

 flowers. In order to reduce the attractive surface, the petals were clipped 

 to half their length, giving the corolla a rotate form, with no spaces between 

 the petals. The flowers used were at the same stage of development, the 

 number of normal and mutilated ones being the same on each day. Table 

 10 shows the effect of this reduction in attractive surface. 



Table 10. — Visits to normal and mutilated flowers. 



The number of visits to the normal flowers was nearly four times as 

 great as to those with the petals shortened. Since conditions were other- 

 wise identical, this not only proves the importance of the corolla in attrac- 

 tion, but also shows that its effectiveness is related to its expanse. The 14 

 inspections were made by Apis and Bombus and indicate that about one- 

 fourth of the visits failed because of the disturbance of the usual perception. 

 This was especially true of B. juxtus, which flew away in 7 different cases 

 when only a centimeter from the flower. Moreover, Apis was forced to 

 change its method of working, since it could no longer walk around the 

 stamen mass on the petals. 



Stamens covered. — The stamens were covered with absorbent cotton 

 in 30 flowers and an equal number of normal ones taken for comparison. 

 Apis visited 25 of the latter, but found the stamens in only one of those 



