30 



MASS. EXPERIMENT STATION BULLETIN 249 



The adult or Beetle is about 1/5 of an inch long and dark brown in general 

 color with black and gray markings. Its wing covers are rough with a 

 noticeable black hump near the middle of each. The whole body covering 

 is hard and strong, and there is no easily distinguishable difference in the 

 external appearance of the male and female. The beak extends forward and 

 then downward nearly perpendicularly to the body. 



LIFE HISTORY AND HABITS 

 Eggs 



Number of Eggs Deposited 



The number of eggs laid by one beetle varies greatly with the vitality 

 of the individual. Weak specimens may lay less than ten eggs during their 

 life, while 557 eggs (9), mostly in plums, have been reported from one very 

 prolific female at Washington, D. C. 



Records of five individual pairs confined with apples in cages at Waltham 

 in 1927 showed an average of 175.75 eggs per female, and 254 eggs was the 

 largest number deposited. The average number of days on which eggs were 

 laid was 41.75, an average of 4.23 eggs per day of laying. The greatest number 

 of eggs laid in one day was 13. 



Length of Incubation Period of Eggs 



The number of days between the laying of the egg and the hatching of the 

 larva varies from 4 to 11, depending largely on the temperature. The first 

 eggs laid in the spring always had a longer incubation period than the 

 later ones. The duration of this period throughout the season in the 

 insectary at Waltham follows: 



Table 4. — Length of Incubation Period of Eggs of the Plum Curculio 



Waltham, Mass. 



Larva 



Habits of Newly Hatched Larva 



In the apple the young larva begins tunneling into the flesh of the fruit 

 very soon after it hatches from the egg. Observations in the insectary 

 indicate that normally they are out of sight two hours after they hatch. 

 The path of the tunnel through the fniit may be exceedingly tortuous but a 

 large number of grubs burrow straight to the core. 



Many small larvae die in the tunnels before reaching the core. In apples, 

 the pressure of the growing fruit is the main cause but other reasons un- 

 doubtedly contribute to this mortality, which is especially noticeable in 

 larvae hatching from eggs laid late in the oviposition period. 



The writer has never seen an apple on the tree from which a curculio 

 larva has emerged unless that apple was ready to fall while small. 



