26 



GEXERAL BIOLOGY 



J- 



The relative fitness of the different visitors to one 



kind of flower. 



It will have been observed in the course of the field studies 

 hitherto outlined, that not all the visitors to one kind of 

 flower are equally proficient in obtaining its stores or in 



transferring its pollen: also, that 

 the manner of visitation is A^ery 

 different in different insects. The 

 butterfly perching atop of a phlox 

 corolla and probing the deep tube 

 only with its long proboscis (fig. 21) 

 could not exchange places with the 

 bee that plunges bodily into the 

 chelone flower (fig. 22): it would 

 '^^^■^^- Diagram of a butter- meet with difficulties like those of 



flv on Phlox, and of the posi- 

 tion of the stamens within the stork of thc fable, attempting 



the corolla tube. . » j- o 



to dine with the wolf. A more 

 careful study of this matter will 

 show that the pollination of a 

 flower may be well effected by in- 

 sects that operate in very different 

 ways. 



The following study of all the 

 visitors to one kind of flower is in- 

 tended to reveal the actual rela- 

 tions existing between a flower and 

 its visitors, and the relative fitness 

 of these visitors. Clearly this fit- 

 ness consists in two things: i) 

 ability to get the food store the flower offers, and 2) ability 

 to transfer pollen from anther to stigma. 



Study J. All the visitors to some common flower. 

 Apparatus needed: insect net, cyanide bottle, lens and 

 note book: use chiefly the two last mentioned. 



Fig. 22 The flower of turtle 

 heads {Chelone glabra), and 

 its visitor (worker Bomhus). 



