The Harvest Flies or Cicadas 



remaining there, isolated from others and moving, probably very 

 slowly, for seventeen or thirteen years. It molts four times, the 

 first time after from one year to eighteen months, the second after 

 two additional years, the third after three years more, and the 

 fourth after another period of three or four years, leaving three or 

 four additional years to elapse before the insect assumes the so- 

 called pupal state. The anterior legs of the larva are curiously en- 

 larged and resemble the cutting jaws of biting insects. They are 

 especially designed for digging and transporting earth. The food 

 which it consumes is obtained probably from the soil humus and 



to some extent from the roots of 

 plants. After the change to the 

 pupal condition the insect bur- 

 rows to the top of the ground 

 and, emerging, crawls up the 

 trunks of trees where the skin 



Fig. 126-Cicadaseptendecim, young ^ jj^^ ^^^ ^j^g gj^,^ -^^^^^^ jg^^g^^ 

 larva. (After Rtley.) ^ 



Occasionally, in certain kinds of 

 soil or when the pupa has reached the surface too early, it will 

 construct mud chimneys from the summit of which it eventu- 

 ally issues. 



in the great cicada year of 1885, Dr. Riley started an interest- 

 ing series of experiments in order to determine whether the 

 duration of the larval stage with the thirteen-year race would be 

 prolonged by transporting the eggs north and accelerated by 

 transporting eggs to the south. This was done on a very large 

 scale and at several localities, the exact locations being carefully 

 marked and recorded. No positive results have as yet been ob- 

 tained; that is to say, no undoubted specimens have issued at 

 either north or south. 



The ultimate fate of this interesting species is undoubtedly ex- 

 tinction and its numbers are rapidly growing less. One of the 

 comparatively few insects upon which the English sparrow feeds 

 with avidity is the periodical cicada and many thousands of them 

 are destroyed by sparrows each time they make their appearance 

 and before they lay their eggs. 



934 



