NATURE'S CRAFTSMEN 



host begins to move. What engineering skill directs 

 their course aloft? What instinct guides their move- 

 ments and enables them with unerring accuracy to 

 burrow to the sunlight? If we suppose that a pupa 

 reaches the surface before it is quite prepared to trans- 

 form, or, when the surface is reached, that weather or 

 other conditions retard the change to the winged form, 

 we have the influences that require it to build a shelter. 

 Its manner of proceeding is interesting and ingenious. 

 It brings up from its burrow a little ball of mud, which 

 it carries between its mouth and strong fore paws. The 

 latter are admirably designed for digging. The pellets 

 are placed atop of one another, as a mason would lay 

 stones while building a circular tower. They are moist- 

 ened by saliva, which serves as a sort of cement, and 

 are pushed down upon each other by the head and feet, 

 and thus adhere tenaciously. The inside is smoothed 

 by continued motion of the jaws, as a plasterer spreads 

 mortar upon a wall. It is not varnished, however, as 

 some naturalists have asserted. The top is closed, and 

 the builder awaits within nature's signal to emerge, 

 whereat it breaks through the top, or occasionally the 

 side wall. Like a frontier pioneer, it leaves its house 

 and moves on, joining the mighty procession of its 

 migrant fellows. The huts stand empty in the silent 

 cicada city, like an abandoned mining-town whose 

 "boom has burst," or like the winter-quarters of an 

 army when the spring campaign calls afield. 



Beneath the surface of the area occupied by our city 

 brood, as shown by deep section cuttings, the earth was 

 a net-work of crossing and interblending burrows. It 

 would seem that the normal preference of the pupae was 

 each for its own ascension track. One fancies that this 



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