GENERAL RESUME. 245 



creased the number of visits to natural flowers and had practically no effect 

 upon those to artificial ones. In the majority of cases it actually decreased 

 the number of visits, often as much as ten times. Wery found that honey 

 remained practically untouched in competition with natural or artificial 

 flowers, obtaining such ratios as 49:0 and 25:0, and emphasized the fact 

 that honey attracts bees very little. 



Effect of added odors. — In his first studies of the effect of adding odors 

 to flowers Plateau obtained no conclusive results. Thyme and sage appeared 

 to attract feebly, lavender not at all, and mint to repel. In his later studies, 

 he stated that it was indispensable for good results to avoid essences and 

 to employ substances known to attract. With these he had marked success 

 with but one or two, such as anisette, a sugar sirup flavored with anise. 

 On the other hand, our experiments showed a decrease of 50 per cent in 

 the number of visits when various perfumes and essences were added, even 

 in the presence of honey. With occasional exceptions, perfumes in them- 

 selves have no effect in increasing attraction, though they may serve as 

 indicators of the presence of honey or sirup and thus seem to be attractive, 

 as in Plateau's results. It is possible that positive results would be secured 

 by using perfume from flowers that bees had been visiting in other areas or 

 earlier in the season, and such experiments are now under way. 



Relative value of color and odor. — Wery has endeavored to give 

 quantitative expression to the respective parts played by color, form, odor, 

 and food in the attraction of insects, and her values seem to be fair approx- 

 imations of the various roles. Her general conclusion in this respect was 

 formulated as follows : 



"For the honey-bee the attraction exerted by the form and color of flowers is ap- 

 proximately four times greater than that of their pollen, perfume, and nectar taken 

 together. Thus, if the total attraction exerted by the most attractive flowers is taken 

 as 100, that of form and color will be represented by about 80 and that of the other 

 three factors by about 20." 



In view of the faint sense of smell for honey and pollen exhibited by bees, 

 this seems a conservative figure except for flowers with a marked perfume, 

 which are still to be adequately investigated. It is these flowers that have 

 given rise to contradictory opinions as to the relative share of color and odor 

 in attraction from a distance and guidance near at hand. 



FORM. 

 Distinction and role. — Following the views of Exner as to vision, both 

 Plateau and Forel were of the opinion that insects distinguish forms more 

 or less vaguely, except when in motion. When one recalls the incessant 

 activity of bees on flowers, this exception is nearly tantamount to the 

 admission that insects do distinguish forms and make use of them in deter- 

 mining their visits. Although Perez regarded form as less important than 

 color or odor, he pointed out the contradiction involved in Plateau's con- 

 tention that insects could not distinguish colors, but that they were guided 

 to buds, withered flowers, and fruits by their form. Moreover, Forel stated 

 that wasps readily recognize the forms and contours of objects, and he 

 demonstrated that wasps and bumble-bees could distinguish bands from 



