88 THE PLUM CURCULIO. 
same soil in the laboratory do not differ essentially, though 5 larvee 
went to a depth of 24} inches, oneto 24inches, andtwo to3inches. The 
above figures are patter shown in Table XLIV, which includes also 
records on 40 larve at the insectary in Washington, obtained by use 
of a soil box, under natural conditions, the soil being a sandy garden 
loam. 
Taste XLIV.—Showing depth to which larvx of the plum curculio enter soil for pupation, 
various localities. 
{ 
Me laoeal a Fa eae (eo ea eee al ee 
Localities. q aq q | 3) 3) fe | Se Sei Celery |S 3 = 
Ei fae ee a ee se ec ele saieea cellule: |: 
nit nis ost smn n+ na os Pe ni nie 
rit nil colt | bam! mo m N nN N nN of oD oO ‘= 
Illinois 
Ves opeaoone|lbeoae 45 55 40} 19 16 3 UL 2) srs tall se tlhe eal eaten | Meet eee 179 
LOOSE Seinen 48 137 100 91 50 77} 39) 51 14} 15] 12 8 1 2 645 
Georgia: 1906... -- 34 61 34 21 23 11 17 10 5 IM asose 2 Sars eer 219 
District of Co- 
lumbia: 1905...- 1 3 7 | Ky) 6 ZL ate 1 1 See 2)1| sere |----- 40 
Totals. 4- 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 We 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 larvee 
pupate comparatively ciose 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 destroying the pupz by timely and pr Opes 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. 
