50 X. H. AGR, EXPERIMENT STATION. [Bulletin 171 



In general, if the fruit in question is of sweet flavor or attractive 

 aroma, there seems to be only one factor of consequence deter- 

 mining the number of punctures per apple. That factor is the 

 relative abundance of female flies in or about the tree as compared 

 with the amount of fruit available. If the circumstances of 

 previous seasons have brought about a large supply of flies, and 

 if there is a less than ordinary amount of fruit, the fruit is apt to 

 be most thoroughly punctured. If the reverse is the case, in- 

 festation is likely to be slight. 



The maximum number of egg punctures found in any one 

 apple in the entire investigation was observed in a lot of Porters 

 picked September 10, 1913. The entire lot was badly infested, 

 many apples having more than 20 punctures each. One apple 

 in the lot had 46 punctures. This is a tree that had been sprayed 

 with poison bait, receiving 7 applications from July 9 to Septem- 

 ber 6. The detail record will be found in the discussion of 

 poison bait spraying. 



PERIOD DURING WHICH EGGS ARE LAID. 



As noted in the discussion of the length of the period after 

 emergence before egg-laying begins, flies may begin to lay eggs 

 within a week or less after they emerge. Thus, with emergence 

 beginning under favorable conditions the last week in June, or 

 under circumstances that tend less toward acceleration the first 

 or second week in July, the beginning of the egg-laying period 

 may be set down as the first to the fifteenth of July in the average. 



Through the experiments described below, with field obser- 

 vations to corroborate the results, it is certain that the end of the 

 egg-laying period does not come until well into September, or 

 probably until frosts and other climatic conditions bring to a 

 close the life of the female flies. 



In 1910 an egg-laying period was definitely proved extending 

 from July 4 to September 19, inclusive, a total of seventy- 

 eight days. 



Experiments in igio. The following preparations were made 

 in 1910 for securing data as to the length of the period during 

 which egg-laying may continue in an ordinarj^ orchard. 



In an orchard at Durham two Tolman Sweet trees were 

 selected, and bags of cheese-cloth were placed over clusters of 



