39 



we will find that they lead right back to some of the insects. 

 In fact, insects seem to be everywhere and in everything 

 sometimes pla3'ing an useful part but more often a destruc- 

 tive one. 



As those milkweeds along the wall seem to be so attrac- 

 tive to the bees and butterflies we will give them some of 

 our attention too. There are several siaecies of milkweed, 

 some with white flowers, some with purple, cream-color and 

 orange. Most abundant of these is the 



COMMON PURPLE MILKWEED. 



The pretty, drooping clusters of lilac-colored flowers 

 have a very sweet odor, so sweet that many people do not 

 like it. They are favorites of many insects though, for 

 ■within each flower are five little cells or cups, each over- 

 flowing with nectar or "honey". 



Commonest among its butterfly visitors is the large black 

 and red kind shown in the little colored picture. This is 

 called the "Milkweed Butterfly" because it likes these flow- 

 ers so well and because its caterpillar feeds upon the leaves 

 of the milkweed. The milky juices of milkweed are very 

 bitter; it is supposed that these give a disagreeable taste 

 to both the caterpillar and to the butterfly for few birds 

 will eat either of them. 



We have shown earlier in this book that pollen from one 

 blossom must be transferred to the stigma of another in 

 order that the seed may be fertile, or capable of growing 

 other plants, and that in many cases it was necessary for 

 insects to do this. Milkweeds have a very clever and inter- 

 esting arrangement to force insects to work for them. 

 An insect in moving about on the flower gets his leg 

 caught in one of the five clefts at the base of the 

 flower; it easily slides up the slot and catches firmly in 

 a tiny notch on the slender stalk that connects two little 

 pollen masses. In order to get free, the insect must tear 



