1 2(5 



THE FACTORS 



[Part I 



is a rather large black bird, unfortunately undetermined, which eats the 

 petals greedily. 



ii, ENTOMOPHILOUS FLOWERS. 

 The number of flowers adapted for pollination by insects is far greater 

 than that of flowers adapted for pollination by birds, even in places 



where there are ex- 

 cellent pollinators 

 among the birds. 

 Whilst however or- 

 nithophily shows a 

 restricted range of 

 distribution, entomo- 

 phily has been proved 

 to exist in all floras, 

 even up to the limits 

 of phanerogamic ve- 

 getation. Only three 

 classes of insects are 

 specially active as 

 pollinating agents, 

 Diptera, Lepidoptera, 

 and Hymenoptera, 

 whereas other insects 

 are either of no im- 

 portance or of merely 

 subsidiary importance 

 in this respect, and 

 appear to have called 

 forth no specially 

 adapted form of flow- 

 ers. The three most 

 important groups of 

 pollinating agents are 

 however present 

 wherever flowers exist, 

 and have everywhere 

 caused adaptations 

 through natural selection ; but their relative numbers are often very 

 unequal, and this inequality repeats itself in the relative number of 

 flowers specially adapted for pollination by Diptera, Lepidoptera, and 

 Hymenoptera respectively. A comparison between cold, temperate, and 

 warm districts, or between islands and continents, is often very instructive 

 in this respect. 



Fig. 64. Feijoa Schenckiana. An omithophilous myrtaceous 

 plant from Santa Catharina, Brazil. Natural size. 



