THE SEVENTEEN- YEAR LOCUST. 
By R. E. Snodgrass. 
Office of Deciduous Fruit Insect Inrestigations, Bureau of Entomology. 
[With 5 plates.] 
UNDERGROUND LIFE. 
Most of our familiar insects are regulated in their changes by the 
seasons of a single year. Hence we marvel at the 17-year life of the 
periodical cicada, the insect generally known as the IT-j^ear locust. 
Yet there are common insects that normally take tw o or three 3'ears 
to reach maturity, and certain beetles have been known to live for 20 
years or more in the larval stage, though under conditions adverse 
for transforming to the adult form. 
Still there is something about the cicada that stirs our imagina- 
tion as no other insect does. For nearly 17 ji'ears it silently toils in 
dreary tunnels underground. Then a springtime comes when 
countless thousands of the creatures issue from the earth, undergo 
their startling transformations and swarm into the trees. Now the 
very air seems swayed with the monotonous rh}i:hm of their song, 
while the business of mating and egg laying goes rapidly on till the 
twigs of trees and shrubs are everywhere scarred with slits and 
punctures where the eggs are placed. In a few weeks the swarm is 
gone, and we may not live to see their progeny return. 
Different insects undergo various degrees of change as they pro- 
gress from youth to maturity. Some, like the grasshoppers, change 
comparatively little; otiiers, such as the moths and butterflies, go 
through three utterly dissimilar forms. The cicada is intermediate 
between these extremes. Its young is a tough-skinned creature 
(pi. 1) having the front feet specially formed for digging, but other- 
wise, aside from lacking wings and external organs for reproduction 
and &gg laying, it is not radically different from its parents. It 
feeds, by means of a piercing and sucking beak, on the sap of the roots 
amongst which it burrows, in the same manner as the adult feeds on 
the sap in the twigs and branches of the trees amongst which it spends 
its life. 
Of the underground life of the young cicada we still Imow very 
little. The fullest account of its history is that given by Dr. C. L. 
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