RELATED STUDIES AND CRITIQUES. 189 



could not go directly to each one. However, several facts argue against this 

 assumption. The bees behave in the normal manner even when the flowers 

 sway back and forth in a strong wind. Spraying menthol in the nectaries 

 does not change the behavior, except that the bees fly away after probing 

 such a nectary or go rapidly to the next. Moreover, the layering and the 

 concentration of the nectar odor above the nectaries must be obliterated 

 by its mixing with the odor of the flower itself. 



Detto also gave an interesting account of the training of an individual 

 bee, which was effected by covering a flower cluster with glass. The cluster 

 was thus changed by the addition of the glass, the greater accumulation 

 of nectar in consequence of fewer visits, and a corresponding increase of 

 fragrance. The abundance of nectar appeared to be the chief factor in the 

 association through which the bee gradually accustomed itself to the new 

 marks of the cluster and finally came to gather nectar from it almost 

 exclusively, so that it might be said to know it. 



The following general statements were made with respect to the sigifi- 

 cance of color in the attraction of bees: 



1. The assumption of Sprengel, Darwin, Mueller, Buttel-Reepen, and others that the 



color of the flower brings about the attraction of the higher bees, Apis and 

 Bombus, has been established by the investigations of Forel, Andreae, and 

 Giltay. 



2. However, since flowers 'with inconspicuous corollas are often abundantly visited 



by honey-bees and bumble-bees (Ampelopsis, Vitis, Rhamnus frangula, Coton- 

 easter acutifolius, etc., with greenish flowers), the bright color of corolla or 

 inflorescence is not an indispensable condition. Still, color must play a sig- 

 nificant part in the competition of species for the visits of the most dependable 

 pollinators, since striking colors are more easily found than dull ones and since 

 these insects orient themselves in flight exclusively with their eyes (Buttel- 

 Reepen, Forel). 



3. The return of a habituated bee to the plant is independent of the color signal, 



probably indeed after the first visit, since the bees are able to refind the place 

 of the desired plant through optical orientation to the surroundings (Buttel- 

 Reepen, Giltay, etc.). 



4. Guidance to the individual flowers of an inflorescence takes place by means of 



vision. Normally the color of the corolla is the chief factor in guiding the bees 

 to the single flowers. Sometimes other features of the flower have a share in 

 this, and the removal of the corolla does not necessarily cause a cessation of 

 visits. 



5. The distinction of flowers of the same color but different species by the honey-bee 



is very probably due to the perception of odor when near at hand. 



6. It is very probable that honey-bees and bumble-bees locate the nectaries of large 



flowers by means of vision. 



Chance observation of visits to imitations. — Plateau (1906:148) 

 has collected the records of the great majority of accidental observations of 

 visits to artificial flowers on hats, flower designs on tapestry or wall-paper, 

 and bits of colored paper or cloth. To these a few others are added here to 

 make the record complete and to permit a discussion of their significance in 

 the light of Plateau's criticisms. The first recorded instance of such visits 

 appears to have beeen made by Houzeau (1872:132), who stated that 

 Trevillian saw an individual of Sphinx convoluta fly along wall-paper orna- 



