108 A NATURALIST IN THE GREAT LAKES REGION 



blossoms so the nectar may be reserved for the flying forms that 

 alone serve the plant in polination. The wild pink accomplishes 

 the same object by rings of sticky substance exuded on its stem 

 at the nodes. Flowers with long tubular corollas like evening 

 primrose, trumpet vine, and Jimson weed are so deep that only 

 insects with long sucking tubes like the moths and butterflies 

 can reach the nectar, though sometimes the bumblebee bites 

 through the base of the blossom and steals a meal. The hound's 

 tongue, whose blossom is the color of aging 

 meat and which has a corresponding odor, 

 is visited chiefly by flies that seem partic- 

 ularly adapted to enjoy its sweets and to 

 transfer its pollen. Sometimes a flower is 

 so constructed as to require the presence 

 of a single sort of insect to take out and 

 carry its pollen; such is the case with 

 the Yucca, grown as an ornamental plant 

 in our gardens and dependent on the 

 yucca moth that is always associated 

 with it. 



On the blossom clusters of a fall aster 

 FIG. 66 Cup formed with wn ite-ray flowers and yellow-disk 



about the stem at base of -111 



leaf petioles, Silphium flowers one often finds a spider that has a 

 perfoliatum, the cup yellow body and white legs. Lying thus 

 concealed by its harmonious coloring, it 

 pounces on the visiting flies and so secures its food. 



There is a plant louse or aphid that feeds on the roots of our 

 common field corn. It in turn furnishes to the common brown 

 ant a fluid excretion that serves -as food and seems to be highly 

 prized. The ant takes the eggs of the aphid into its burrows in 

 the fall, rears the aphids, and in the spring sets them out to feed 

 on the tender shoots of weeds until such time as the corn germi- 

 nates, when they are transferred by the ants to the corn roots. 



Light is an important factor in the distribution of animals. 

 Thus many species inhabiting the ground, the subterranean 



