THE PEAR LEAF-WORM. 



subjected to a large amount of heat and desiccation. Thus it is 

 evident that the larva and its cocoon must be able to withstand 

 considerable dryness. An experiment was performed at Wenatchee, 

 Wash., to learn whether moisture was necessary to the larva. 

 Cocoons were collected from the soil within a few days after they were 

 spun, in May, 1914, and divided into two lots, both of which were 

 kept on the surface of some soil in jelly glasses. The soil in one lot 

 was kept moist by pouring water through a glass tube inserted in the 

 soil. The other lot was allowed to remain dry. The first lot was 

 kept moist until September. After this both lots were left untouched 

 until spring, being kept over winter in an unheated room. During 

 the emerging period the first lot was again kept moist, while the 

 other remained dry as before. As a check on these lots the emergence 

 from a third lot, collected April 3, 1915, was recorded. Table I 

 gives the results of this experiment : 



Table I. — Adult emergence of fear leaf-worm from moist and dry cocoons, Wenatchee, 



Wash., April, 1915. 



Observation. 



Moist. 



Dry. 



Cocoons col- 

 lected Apr. 

 3, 1915. 



Total. 



Number of cocoons. 

 Numoer emerged. . 

 Per cent emerged. . 



59 

 51 



86.4 



194 

 118 



55 

 31 

 56.4 



308 

 200 



64.9 



From Table I we learn that 86.4 per cent emerged from cocoons 

 kept moist during the previous summer, 60.8 per cent from dry co- 

 coons, and 56.4 per cent from the cocoons collected April 3, 1915, and 

 which were thus under natural conditions during practically the whole 

 period; the total percentage emerging was 64.9. The cocoons of the 

 dry lot that did not give adults were examined later, and a number 

 of them contained fully-formed adults that had been unable to break 

 through the tough, dry cocoon. This indicates that the smaller per- 

 centage of adults emerging from these cocoons was due to the dryness 

 at the time of emergence rather than the dryness during the preced- 

 ing summer, and perhaps collective dryness weakened the insects 

 somewhat. The larvae had lived through the dry period of the sum- 

 mer, had pupated the following spring, and the adults had cast the 

 pupal skin, but had been unable to get through the dry cocoon. 



ITie smaller emergence from cocoons collected in April, 1915, is 

 explained by the more uneven conditions to which the"^ had been 

 subjected, such as the freezing and thawing of winter. 



The newly-molted j)upa is entirely pale green, with black eyes, and 

 mcHsures about 5 mm. by 1.7 mm. Shortly before the time for the 

 adult to emerge the pupa turns dusky blackish, with the wings, fore- 

 legs, and portions of middle and hind legs ycillowish. VentraUy the 

 abdominal rings and the saw case of the female are greenish. 



