462 PROFUSION OF SAP. 



ivood hy the " locust of the seventeenth year " — Cicada 

 septemdecini. This is a most remarkable beetle, ap- 

 pearing only once in seventeen years. There are 

 six or more broods of them in this country, which 

 have their distinctly defined routes ; and while the 

 length of time from the first to the second appear- 

 ance of each brood is always seventeen years, yet 

 these seasons are not identical in the different 

 broods. One of them appeared in 1843 ; another 

 in 1847. They utter a note considerably prolonged, 

 the middle of which is piercingly shrill. They do 

 not seem to be very discriminating as to the species 

 of plant which they attack. Dr. Fitch, entomol- 

 ogist to the State of New York, said that the tops 

 of the forest trees for more than a hundred miles 

 seemed as if they had been scorched by fire, a 

 month after these beetles had left them. The injury 

 was done by the deposition of the eggs. The female 

 punctures the wood, making a cavity large enough 

 to contain al^out twenty eggs, and continues to lay 

 in this manner from four hundred to five hundred 

 eggs. From these punctures the sap weeps, weak- 

 ening the limbs, and often causing, ultimately, their 

 death. The larvae penetrate the earth to a consid- 

 erable depth, sucking the sap from the roots of all 

 sorts of plants (Fitch). 



IV. Diseases which affect the Tree gener- 

 ally. 1 Profusion of sap — Profusio simplex. 



