126 



THE FACTORS 



[Part : 



is a rather laro-e black bird, unfortunately undetermined, which eats th( 



petals greedily. 



ii. ENTOMOPHILOUS FLOWERS. 



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

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



where there are ex 

 cellent pollinator 

 among the birds 

 Whilst however or 

 nithophily shows 

 restricted range o 

 distribution, entomo 

 phily has beenprove( 

 to exist in all floraj 

 even up to the limit 

 of phanerogamic ve 

 getation. Only thre 

 classes of insects ar 

 specially active a 

 pollinating agent; 

 Diptera, Lcpidopter; 

 and Hymenopter; 

 whereas other insect 

 are either of no iir 

 portance or of mere! 

 subsidiary importanc 

 in this respect, an 

 appear to have calle 

 forth no speciall 

 adapted form of flo\\ 

 ers. The three mo; 

 important groups i 

 pollinating agents ai 

 however preser. 

 wherever flowers exisj 

 and have e\-erywher 

 caused adaptatioi 

 through natural selection ; but their relative numbers are often ver 

 unequal, and this inequality repeats itself • in the relative number ( 

 flowers specially adapted for pollination by Diptera, Lepidoptera, an 

 Hymenoptera respectively. A comparison between cold, temperate, an 

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

 in this respect. 



^ 



"H 



Fig. 64. Feijoa Schenckiana. An omithophilous myrtaceons 

 plant from 'Santa Catharina, Brazil. Natural size. 



