GERANIUM. 



109 



similar in color and size. As there were 25, 10, and 5 respectively, the 

 corresponding numbers for visitors and visits are 11:26, 45:90, and 10:10, 

 the much larger nectar supply of Aster giving it a great advantage. 



Table 75. — Natural competition: Geranium, Aster, Allium, Campanula, Heracleum. 



Summary. — In these two experiments the preferences of most of the 

 visitors were so pronounced that the usual difference between plant and 

 bouquet is hardly to be seen. Anthophora, Bombus, and Osmia were the 

 only visitors to work on both standard and bouquet, the first two giving 

 preference to the rose and the last to Pentstemon secundiflorus. Andrena 

 and Megachile likewise preferred the rose, while Apis selected Geranium. 

 The competition between Geranium and Castilleia was conclusive as to the 

 marked specialization of the latter, the broad-tailed humming-bird being 

 the regular pollinator and Osmia the only insect to visit it. As in former 

 experiments, Pentstemon barbatus was entirely ignored, perhaps because of 

 its narrow vermilion corolla, and the difference between P. secundiflorus 

 and Scrophularia was less than would be expected from the size and color 

 of the former. In both experiments more individuals of Pseudomasaris 

 went to Scrophularia, but they made a larger number of visits to Pentstemon. 

 Osmia, however, showed an all but exclusive preference for the latter. 

 In the second experiment the bouquet was later turned so that the flowers 

 of P. barbatus were in the position formerly occupied by Scrophularia. 

 Pseudomasaris returned to the original position of the latter, recognized 

 its mistake, and then flew through the red flowers of the Pentstemon to the 

 figwort. Andrena crataegi flew 7 times within 0.5 cm. of Scrophularia 

 and 4 times around P. secundiflorus, but ignored P. barbatus; it then flew to 

 Rosa and alighted. 



Since there were four times as many roses and twice as many castilleias 

 as geraniums, the latter was relatively as attractive as the others, receiving 

 more visitors but fewer visits than the rose. The three species in the 

 bouquet were represented by an equal number of spikes. Pentstemon 

 secundiflorus was about 50 per cent more attractive than Scrophularia, 

 probably owing to its much larger size and brilliant color. 



