30 Nebraska State Horticultural Society. 



quently development of larvae and decay go on together. Badly de- 

 cayed apples have in most cases furnished the largest and most vigorous 

 larvae, and we have come to regard the rotten pulp as the food most 

 acceptable to the larvae of the plum curculio." 



"There' is considerable mortality among larvae while within the 

 fruit. Extended observations through two seasons point to two possi- 

 ble causes: 



First — Crushing by growth of fruit. The writer holds the opinion 

 that some larvae die from this cause, and this opinion is based upon 

 miscroscopical examination of larvae found dead in the burrows, and 

 examination of the fruit tissue surrounding these larvae. Many larvae 

 thus found have a flatttnied, crushed appearance. This, taken ih con- 

 nection with the fact that newly formed cells closely encompased the 

 'larvae and completely closed the burrows behind them, is looked upon 

 as fairly good evidence that death resulted from pressure from growing 

 fruit cells. The eggs of the plum curculio are deposited in apples on 

 the trees. If the apples fall at the time the eggs hatch, or soon after, 

 growth of the fruit is arrested, and development of the larvae may 

 proceed; but if the fruit fails to fall, growth of tissue continues and 

 the formation of new cells may be so rapid and strong that the weak, 

 newly hatched larvae cannot overcome it and hence are crushed. 



Second — The action of direct sunlight upon fruit. Considerable 

 evidence has been gathered tending to show that sunlight on fallen 

 apples is destructive to the contained larvae. No living larvae were 

 found in fallen apples that had been exposed to the sun for a few 

 tours, while apples taken from under the shade of trees gave a fair 

 proportion of living larvae. 



DEPTHS TO WHICH LARVAE GO FOR PUPATION. 



The larvae, having remained in the apple an average of twenty 

 (lays, enter the ground to a depth of from one-fourth inch to three and 

 one-half inches, depending on the character of the soil and other con- 

 ditions. Most of them enter the soil to a depth of from 1 ^/^ to 2% 

 inches. This point is of value in determining the depth to which the 

 disc must be run to disturb the larvae during pupation. The average 

 length of time for pupation has been found to be 28 days. There is, 

 therefore, 28 days' time during which they may be disturbed by the disc 

 or other methods of cultivation. 



The most pupae are in the earth from the middle of June until 

 perhaps the middle of August, although some may reniarn as late as 

 November. The average number of eggs deposited by each female 

 beetle is 231. "Newly emerged beetles usually remain quiet for a time. 



