CICADIM. 
719 
emerges. These empty skins are a common feature in the hills. 
(Fig. 495). The length of the life-history is unknown, though one 
Fig. 495.— (JOSMOPSALTRIA NATURATA. NYMPH. 
American species is known to live seventeen years, the imago only 
appearing for one summer, the nymphs living for sixteen years. 
Fig. 496.— Platyplrura mackinxoni. 
Cicadas are dependent upon 
trees for food, so far as is 
known, and occur most abun¬ 
dantly in forests and well- 
wooded moist localities. The 
imagos certainly suck the sap 
of trees and are so coloured 
as to be exceedingly difficult 
to see when on tree bark. They 
are known best for the ex¬ 
tremely shrill sustained sounds 
produced by the males, a sound 
which has no rival except in 
the steam whistle. After a 
shower the noise is deafening 
if one is in a forest with many 
Cicadas and the kind of noise 
produced varies immensely 
with the different species. The 
