!9i7] 



ROBERTSON—FLOWERS AND INSECTS 



3" 



The relations of bees and other insects to non-social and social 

 flowers in general (based upon 13,942 visits of 1287 insects to 437 

 flowers) are shown in table II. 



TABLE II 



Lower 



Hymen- 



optera 



Hemip- 

 tera 



Coleop- 

 tera 



Diptera 



Lepid- 

 optera 



Bees 



All 



Except 

 Bees 



Total 



Percentage of visits 



To non-social flowers 

 To social flowers 



44 

 95-5 



6.1 



93-S 



9-3 

 90.6 



13.6 

 86. 3 



22.6 

 773 



32.1 

 67.8 



11. 9 



88. o 



20.7 

 79.2 



Percentage of total visits 



To non-social flowers 

 To social flowers . . . . 



3-6 



20.4 



O. 2 

 O.9 



14 



3-5 



17.8 

 29.4 



9 3 

 8-3 



67.4 

 37-2 



32.5 

 62.7 



99 9 

 99-9 



Of the total visits of bees, 32.1 per cent are to non-social 

 flowers, and these form 67.4 per cent of the total insect visits to 

 such flowers. Of the total visits of other insects to non-social 

 flowers, the percentage is 4 . 4 for lower Hymenoptera, 6.1 for 

 Hemiptera, 9.3 for Coleoptera, 13.6 for Diptera, and 22.6 for 

 Lepidoptera; or a general percentage of n. 9. Since bees make 



over 



luptcict, UI ct gCllCIctl pCIXeilLctgC Ul ll.y. om^t; uccs maivv, 



two-thirds of the insect visits to non-social flowers, it is evi- 



1 * t i * • r% 9 1 * 1 1 ••• /• 



instrumental 



such flowers. 



Of the total visits of bees, 67.8 per cent are to social flowers, 

 so that bees show a strong preference for these flowers also, although 

 not as strong a preference as the Lepidoptera with 77.3, the Dip- 

 tera with 86.3, the Coleoptera with 90.6, the Hemiptera with 

 93 . 8, and the lower Hymenoptera with 95 . 5 per cent. 



One might suppose, with Muller, that the non-aculeate 

 Hymenoptera have had an influence in the development of some 

 primitive flowers, and that these flowers were further modified by 

 the aculeate Hymenoptera, and finally became highly specialized 

 in connection with the development and specialization of the bees. 

 When, however, we look for such flowers, we find only the so-called 

 ichneumon flowers, Lister a ovata and Chamaerarchis alpina, belong- 

 ing to the most highly specialized of monocotyledons. In the 



