COMMON WHITE GRUBS. 9 
parts of Canada it may possibly extend over a period of four years, 
for such is the variation of the life cycle in the closely related Euro- 
pean white grub,’ which has a 4-year cycle in northern Germany but 
only a 8-year one in southern Germany. 
A résumé of the life of the injurious generation of 1912 is as fol- 
lows: Eggs (fig. 7) deposited by the female beetle in the spring of 
1911 hatched a few weeks later, and the young grubs fed the first 
season on decaying and living vegetable matter in the soil. As 
winter approached they protected themselves from the cold by bur- 
rowing deeper into the ground, remaining there inactive until 
the spring of the following vear (1912), when they returned to a 
es gage yt ae ae 
‘ eg a 
Fic. 6.—A cornfield injured by white grubs, Galena, Ill., 1912. (Original.) 
position near the surface, feeding on the roots of such crops as were 
available. In this the second year they did the maximum amount 
of damage. In the fall they again went deep into the soil, to return 
near to the surface in the spring of 1913, where they will feed as 
before on the plant roots until about June. They will then prepare 
oval pupal cells in the ground, become more or less inactive, and 
later change to the pupal or true dormant stage. The adult beetles, 
which will emerge from the pupx a few weeks later, will remain 
in the pupal cells over winter and will emerge the following spring 
(1914) to feed and* mate in the foliage of trees and shrubs and to 
deposit their eggs in the soil for another generation. 
1 Melolontha vulgaris 1. 
15——2 
92170°— Bull. 543 
