38 



MASS. EXPERIMENT STATION BULLETIN 249 



JUNE 



JULY 



AUGUST 



10 15 20 25 30 



10 15 20 25 31 



10 IS 20 2 5 31 



16 

 14 

 12 

 10 



a 



6 

 '^16 



1926 



NUMBER OF FEEDING 

 PUNCTURES - 40.257 



NUMBER OF FEEDING 

 PUNCTURES - 165,846 



Pigrnre 6. Time of Occurrence of Feeding' Punctures in Apples by Over- 

 wintering- PZum Curculio Beetles in the Insectary, Waltham, Mass. 



The number of feeding punctures used in this diagram is computed from a 

 daily record of the actual nuniber of feeding punctures made by 10 beetles 

 retained from each semi-weekly collection by jarring on the dates shown in 

 Pigure 4. The solid areas in the diagram indicate the total percentage of 

 feeding punctures which occurred after the last date shown in the graph. 

 The last feeding- puncture was made on September 1 in 1926, on October 15 

 in 1927, and on November 17 in 1928. 



Time that Larvae Leave the Fruit. 



Figure 7 shows that larvae of the plum curculio first left the apples to 

 enter the soil between June 25 and 30 in 1926 and 1928, and soon afterward 

 in 1927. The greatest number of larvae left between July 10 and 20 each 

 year, and with the exception of two individuals in 1927 all of them entered 

 the soil before September 1. This activity has been very cbnstant during 

 the three years of observation. A more detailed report on the emergence 

 of larvae from dropped apples in the orchard is given in Table 12. 



Emergence of Beetles from Soil. 



Beginning the last ten daj's of July, the beetles emerge from the soil in 

 increasing numbers until they reach a maximum between August 6 and 20. 

 After this point the number decreases rapidly with a few stragglers con- 

 tinuing to appear until early October, as shown in Figure 8. Emergence has 

 been quite constant in these studies. The beetles seek their hibernating 

 quarters between September 15 and October 1, depending on the weathei-. 



