THE PEAR LEAF-WORM. ; 15 
- the larve had hatched by April 24, and the largest number were enter-. 
ing the soil about May 20, giving an average larval period of about 
26 days. The table shows an average of 28.1 days, and the only 
larva that was reared to maturity (No. 3) occupied 26 days from egg 
to cocoon. This is a longer period than at Walnut Creek, Cal. (18.4 
days) where the larve were reared normally on the trees, and a 
slightly shorter period than at San Jose (31.6 days), where the larvee 
were reared under conditions similar to those in Washington State. 
THE COCOON AND PUPA. 
In order to determine how deeply the larve penetrate the earth 
for the purpose of spinning their cocoons, 60 full-grown larve were 
placed in a screen cage sunk into the soil and filled with 7 inches of 
average orchard soil April 30, 1913. By May 3 all the larve had 
burrowed and on June 18 the soil was examined with the results 
enumerated in Table IX. F 
TaBLE 1X.—Depth in soil for cocooning of the pear leaf-worm, Walnut Creek, Cal., 1913. 
Number of | Inches be- 
cocoons low soil 
found. surface. 
46 Otol 
2 1to2 
4 2to3 
1 3 to 4 
Fifty-three out of 60 were thus accounted for, and therefore 88.3 
per cent of the larve spun cocoons. It is evident from Table IX 
that the great majority spin their cocoons not more than 1 inch below 
the surface. In the above instance this majority was 86.8 per cent. 
Table X shows the depth in the soil at which the cocoons are 
spun in Washington. On May 21, 1915, 93 larvee just ready to enter 
the earth were placed in an open jar on top of 6 inches of fairly 
closely packed, moist, sandy soil, which is typical of the orchards 
of the region. In a few days the larve had all disappeared and 
on June 11 the soil was sifted and 71 cocoons were recovered. Thus 
76.3 per cent of the larve spun cocoons, the others being found 
dead near the surface. The depths at which the cocoons were found 
are given in Table X. 
TABLE X.—Depth in soil of cocoons of pear leaf-worm, Wenatchee, Wash., 1915. 
Number of Inches 
cocoons below 
found. surface. 
ise) 
Hues 
NO Hw O 
et ct ect ct 
