THE PLUM CURGULIO IN APPLES 



31 



Feeding of Larva in Apple 



While the larva is feeding and growing it molts or sheds its skin four 

 times requiring about 16 days for this development in the fruit. In 1927 

 one individual lived fifty-three days in the fruit, and five others stayed there 

 more than forty days, but that is unusual as sho^vn by the summary of the 

 insectary studies of this period for three years in Table 5. 



Table 5. — The Number of Days the Larvae of the Plum Curculio Remain 

 in Apples after Hatching. Waltham, Mass. 



When the larva is ready to leave the fruit, it emerges from a round hole 

 usually through the side, and by this time the apple is shrivelled or rotted 

 so that the flesh around the hole collapses. 



Pupa 



Depth of Cell in Soil 



When the larva leaves the fruit it enters the ground and forms a cell. 

 Practically all of these cells have been found three inches or less below the 

 surface of the soil although where hay is spread under the trees, cells have 

 been found as deep as eight inches below the top of the mulch. In these cells 

 the larvae transform to pupae slowlj\ 



Length of Time Spent in Soil 



In Michigan (9), it was found that an average of 12.03 days or 36 per 

 cent of the total time in the soil was passed as a larva before actual pupa- 

 tion occurred. In the studies at Waltham no record of this period was 

 obtained, but it was found that the total time in the soil ranged from 17 

 to 55 days, averaging about 30 days. In 1926 the average time spent in the 

 soil by reared specimens was 31.46 days, and by field collected specimens 

 31.88 days. A siunmary of the records for three years follows. 



Table 6. — Number of Days Spent in the Soil by the Plum Curculio as 

 Larva, Pupa, and Adult. Waltham, Mass. 



There is much evidence that development of the insect in the soil is 

 influenced by moisture, and that if the soil is dry the time spent in the 

 soil is greatly prolonged even causing death. Heavy rain or watering during 

 the time the beetles are emerging immediately increases the number appear- 

 ing, but the rainfall in New England in addition to the usual sod or mulch 



