THE MILKWEED BUTTERFLIES 



The male monarch is the dandy among butter- 

 flies^;- excellence. He is not only trig in figure 

 and gorgeous in color, but on each hind wing he 

 carries a black sachet bag for the allurement of 

 his lady-love. And she is as brilliant as he, but 

 lacks the perfume pockets. " I am monarch of 

 all I survey " is exemplified in the confident, 

 serene flight of this butterfly ; the species is 

 nauseous to birds in both the caterpillar and 

 adult stages, and by their bold actions they show 

 the result of this immunity. But the monarchs 

 have other problems of their own just because 

 the bird problem is eliminated ; for undisturbed 

 they spread and flourished in their native tropic 

 America until it became a question of sufficient 

 food-plants to nourish their numerous progeny. 

 Because of this they began pushing farther north 

 and south during the seasons of plant growth. 

 As they could not endure the northern winter 

 they came north for the summer and went back 

 in the autumn. This northern migration is ac- 

 complished thus : the mother butterfly follows 

 the spring northward as it advances as far as she 

 finds milkweed sprouting ; there she deposits her 

 eggs, from which hatch individuals that carry 

 on the journey, and in their turn lay their eggs 

 as far north as possible. Thus generation after 



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