88 THE PLUM CURCTJLIO. 
same soil in the laboratory do not differ essentially, though 5 larva) 
went to a depth of 2\ inches, one to 2\ inches, and two to 3 inches. The 
above figures are better shown in Table XLIV, which includes also 
records on 40 larvae at the insect ary in Washington, obtained by use 
of a soil box, under natural conditions, the soil being a sandy garden 
loam. 
Table XLIV. — Showing depth to which larvse of the plum curculio enter soil for pupation, 
various localities. 
W 
m 
to 
A 
A 
rZ 
A 
A 
I 
o 
fj 
A 
cj 
f> 
A 
_• 
a 
a 
a 
S 
a 
a 
a 
H 
a 
a 
a 
H 
a 
a 
Eh 
HM 
rfs 
nW 
1-1 
rH 
1-1 
*-* 
<N 
<N 
<N 
<N 
CO 
co 
CO 
Illinois: 
1903 
45 
137 
61 
55 
100 
34 
40 
91 
21 
19 
50 
23 
16 
77 
11 
3 
39 
17 
1 
51 
10 
179 
1904 
48 
34 
14 
5 
15 
1 
12 
8 
1 
2 
645 
Georgia: 1906 
219 
District of Co- 
lumbia: 1905 
1 
3 
' 
' 
10 
6 
2 
1 
1 
2 
40 
Total 
83 
246 
196 
159 
102 
110 
61 
62 
20 
17 
12 
12 
1 
2 
1,083 
Percentages 
7.66 
22. 72 
18.10 
14.68 
9.42 
10.16 
5.63 
5.73 
1.85 
1.56 
1.11 
1.11 
0.09 
0.18 
100 
Of the total of 1,083 larvae, 684, or 63.16 per cent, pupated within 
1 inch of the surface, and 1,019, or 94.09 per cent, within 2 inches of 
the surface. These figures show that the great majority of larvae 
pupate comparatively close to the surface of the soil — within a dis- 
tance of 2 inches — a fact to be remembered as bearing on the possi- 
bility of destro3dng the pupae by timely and proper cultivations, as will 
be later discussed (p. 176). 
SOIL CONDITIONS AFFECTING TRANSFORMATIONS OF THE CURCULIO 
IN THE GROUND. 
Probably no one natural factor, aside from abundance of food, 
exerts a greater influence upon the welfare of the curculio than the 
condition of the soil during its occupancy by the insect, especially 
the degree of moisture. It is a matter of common observation that 
the beetles may long be retarded in their appearance from the ground 
by drought and that after a soaking rain they will come out literally 
in swarms. The necessity for adequate soil moisture for their suc- 
cessful underground transformations and their emergence is doubt- 
less the most important single influence which has prevented their 
spread into the arid regions to the west. As shown under the head- 
ing of geographic distribution, the species has not extended its range 
much west of the one hundredth meridian, which marks, in a general 
way, the beginning of the arid region. 
Some experiments have been made at different times, but espe- 
cially during 1910, to secure data on the influence, on the transforma- 
tions of the insect, of different kinds of soil and of normally moist as 
compared with dry soil. 
