POLLINATION AND FEKTILIZATION 



123 



■^f 



116. Insects as carriers of pollen. Most flowers which re- 

 quire or are benefited by cross-pollination and wliich are not 



wind-jjollinated depend upon 



insects as pollen carriers. It is 



not an overstatement to say 



that, in general, flowers seem 



to have acquired their colors 



(other than green) and their 



odors as means of attracting 



the attention of insects which 



may serve to cross-pollinate 



them. Insects vary greatly in 



their efficiency as pollinators, 



Fig. 112. Pollen-carrying apparatus ^^e Small ones with smooth sur- 



of leg of honeybee faces on the head, legs, and ab- 



A, right hind leg of a honeybee (seen domen, such as ants and many 



from behind and within) ; B, the tibia Uppflp„ narrvincr littlp nollpn 



(«i), seen from the outside, showing the oeeues, carrymg little poiien, 



collecting basket formed of stiff hairs, while beeS, 

 After H.MuUer moths, and 



butterflies often carry considerable quan- 

 tities. Many bees in particular are provided 

 with a special collecting apparatus for 

 pollen (Figs. 112 and 113). Although the 

 portion which they carry to the hive or nest 

 for food is of no use for pollination, much 

 of that which is smeared over the general 

 surface of the body serves to pollinate the 

 stigmas of flowers which they afterwards 

 visit. A good practical illustration of the 

 importance of insect visits is afforded by 

 the case of cucumbers grown in winter 

 under glass. It is found necessary to keep 

 hives of bees in the cucumber houses in 

 order to insure pollination and consequent crops of cucumbers. 

 Some idea of the number of insect visits may be gathered 

 from. the fact that in a single locality dandelion flowers have 



Fig. 113. Eight hind 

 leg of a bee (Macropis) 



The tibia is covered with 



pollen of the common 



loosestrife. Magnified. 



After H. Miiller 



