THE FLOWER AND THE BEE 



perfect flowers attractive to flies. The disagreeable odor might 

 be supposed to be repellant to bees, but sometimes in early 

 spring large numbers of them gather pollen from this source 

 for brood-rearing. The water-arum {Calla palustris), a plant 

 growing in cold bogs, has a handsome white spathe, but the 

 nauseous scent places it among fly-flowers. (Fig. 78.) 



Among flowers with unpleasant odors the saxifrages are 

 highly interesting, not because flies are the most numerous 

 visitors, but because the white corolla is covered with many- 

 colored dots. The white petals of the round-leaved saxifrage 

 {Saxifraga rotundifolia) are sprinkled with round dots, the outer 

 of which are intense purple red and the inner yellow. The snow- 

 white flower of the star saxifrage (S. siellaria) are beset with 

 purple dots and adorned with two orange-yellow spots. >Sa.r2*- 

 fraga hryoides is white with many shining yellow dots. (Fig. 

 79.) The large golden-yellow flowers of 8. aizoides are marked 

 with numerous orange-red dots, and are visited by 85 different 

 species of flies; all of these spotted flowers are indeed very 

 frequently visited by flies. Mueller believed that the dots 

 attracted the attention of flies more than of other insects. 



There is another group of fly-flowers, the pitfall-flowers, 

 which rely partly on deceptive odors and colors, and partly on 

 pitfalls, which are veritable prison-traps — often death-traps— to 

 various unwary flies. The spotted arum {Arum macidatum) of 

 Europe is a prison-flower and, like all the Aroids, has an offensive 

 odor. The spathe, which is broad above, is constricted in the 

 middle into a neck, below which there is a bulbous cavity com- 

 pletely ensheathing the lower part of the club-shaped flower- 

 stalk, or spadix. In the neck or entrance to the chamber there 

 is on the spadix a ring of bristles with the points inclined down- 

 ward, a little below this a band of staminate flowers, then an- 

 other ring of hairs, beneath which are the pistillate flowers. 



164 



