114 



COMPETITION AND CONSTANCY. 



species, P. halli and P. unilateralis, fared as well or better than the others, 

 the neglect of the third, P. barbatus, obviously being due to its color or 

 shape. When combined in one bouquet, P. glaber was several times more 

 attractive than both P. halli and P. glaucus and about twice as attractive 

 as Elephantella. While Osmia and Prosopis were both attracted by the 

 latter, the one merely hovered and the other was unable to probe the 



Table 80. — Natural and bouquet competition of Pentstemon gracilis. 



tightly coiled beak. Though P. glaber attracted more species than gera- 

 nium, the preference of Apis for the latter gave it the lead. In the natural 

 competition of Pentstemon gracilis and Geranium caespitosum the ratios 

 were 38:8 and 16:16 on days about a week apart. This was due chiefly 

 to the practical dropping out of Osmia and Prosopis in the second case. The 

 results with bouquets and vials followed the rule, neither Pentstemon nor 

 Rubus being visited when it was the bouquet and Chamaenerium flowers in 



