164 
Relation to Soil and Subsoil. 
It is a matter of common opinion that injuries by white-grubs 
are more serious on the higher, hghter, and drier parts of our culti- 
vated areas than on the lower and moister parts, but no exact ob- 
sevations have been made to show whether this apparent difference 
is real under all conditions, and whether, if so, it is due to a greater 
abundance of the grubs on high lands than on low, or to a lesser 
'average power of recuperation and resistance on the part of plants 
growing in comparatively light and less fertile soils. 
I began in 1904 and 1905 to accumulate data on this and allied 
points, by having collections of white-grubs made by persons follow- 
ing the p\o\y, who recorded for each field and situation the number 
of grubs found in each quarter of a mile of furrow. A record was 
also made, for each field examined, of the succession of crops it had 
borne for the five years preceding, of the character of the soil, the 
lay of the land, the conditions as to drainage and to fertilization, 
and the relation of the field to trees and shrubs on which the parent 
beetles of the grubs might have found food. Collections were made 
on this plan from seventy-nine fields in the following twelve counties 
of central and southern Illinois : Stark, Peoria, Woodford, Mc- 
Lean, Champaign, Macon, Macoupin, St. Clair, Washington, Ma- 
rion, Jackson, and Union. This work was interrupted by lack of 
funds and by diversion of assistants to more pressing problems 
before any sufficient mass of data had been obtained to enable me 
to draw satisfactory general conclusions on any one of the points of 
principal interest. So far as they go, they show that the grubs were 
more abundant on the higher and drier parts of the country than on 
the lower and moister parts, and that the fewest eggs were laid by 
the parent beetles in corn fields and the most in grass-lands. Thirty- 
eight low-land fields gave an average of 21 grubs exposed in a mile 
of plowed furrow, and 41 of the high-land fields an average of 31 to 
the mile. The three largest numbers found in any fields were 208, 
164, and 140 grubs to the mile, all on high ground. The largest num- 
bers in any of the low-land fields were 112 and 104 in two of them. 
Ag-ain, the average of fields which had been in corn continuously for 
at least three years preceding was 17 grubs exposed in each mile of 
furrow, and that of fields which, although in corn at the time, had 
been in grass for several years preceding, was 37 grubs to the mile. 
It is evident that useful information may be obtained from data of 
this description if they are accumulated in sufficient number and are 
properly classified. 
II 
