244 PRINCIPLES AND CONCLUSIONS. 



marked and often persistent choice for the proper color, but that there is 

 a general preference for blue. In field and garden, differences in color are of 

 great importance in attraction, but the bee discriminates among them only 

 when it is to its advantage to do so, as between species, or between partly- 

 open buds or old flowers on the one hand and fresh ones on the other. When 

 the flowers differ in color alone, the bee has learned that this is unimportant 

 in comparison with odor and form. When a new factor is interjected, how- 

 ever, as in the case of flowers habitually visited which are changed by 

 painting them with water-colors, a preference is manifested until experience 

 again shows that it is undesirable or unnecessary. 



ODOR. 



Masking or covering flowers to conceal color. — Plateau thought to 

 have demonstrated by masking flowers and heads with paper or green leaves 

 that color is of little or no value in attraction and that odor alone is suf- 

 ficient. Most of his experiments lacked checks or controls, and were con- 

 tradicted by those of Forel, who found that flowers completely masked 

 received no visits. Wherever a slight gap permitted entrance, bees soon 

 found their way in and then returned regularly by the same route. More- 

 over, after the lapse of several hours they discovered the flowers and then 

 visited them normally. Andreae frequently employed beakers masked with 

 dark paper to determine the effect of odor alone; in three representative 

 cases the ratios for color and odor were 10:0, 31:1, and 35:3, indicating 

 that odor is much less effective than color as a rule. Wery noted 32 visitors 

 to normal flowers to 7 for similar ones hidden in foliage, and 19 to artificial 

 flowers fully exposed to but 4 for those concealed in leaves. Giltay repeatedly 

 masked flowers with pots so that no color was visible, but the odor 

 could regularly escape; such blossoms received no visits, but bees came 

 readily as soon as the pot was removed. When petals were placed in a dish 

 and covered with a pot so that they were invisible but the odor could escape 

 they were never visited, but after the pot was removed, bees alighted on 

 them, sometimes immediately. Allard concealed a cotton blossom so that 

 it was visible only from above; this obtained but 1 visit to 12 for the control. 

 When the disguise was taken away, the flower was inspected more than the 

 control. 



These experiments leave no question that for the flowers concerned 

 at least the role of color in attraction is usually several times and often 

 many times greater than that of odor. 



Odor of honey. — While honey has a strong attractive power, this is due 

 chiefly to its sweetness and but little to its odor, especially in the case of bees. 

 Even Plateau had remarked the fact that bees have a weak sense of smell 

 for honey, and this inability has been emphasized by Forel, Buttel-Reepen, 

 Giltay, Wery, Detto, Lovell, and others. Bombus and Apis have repeatedly 

 been observed to pass within a few millimeters of honey in both natural and 

 artificial flowers without perceiving it. In some cases they have even 

 become entangled in it and tried to clean it off without recognizing it. 

 Moreover, sugar sirups and other sweet liquids without odor have often been 

 found to be quite as attractive as honey. Once found, honey is a powerful 

 incentive to return until it is exhausted. In our experiments it never in- 



