56 MASS. EXPERIMENT STATION BULLETIN 355 



years and the low price of apples caused many of the growers to curtail their 

 spray program and give less attention to orchard environment. As a result, 

 large numbers of flies were present in the orchards late in the season and caused 

 a heavy infestation of late varieties. The record of emergence of apple maggot 

 flies made by Professor VVhitcomb at Waltham is as follows: 



Date of Emergence of Apple Maggot Flies from Cages, Waltham 



In Sun— Light Soil 



Cultivated Sod 



1st fly ■ June 22 July 5 



25% flies July 7 July 13 



50% flies July 11 July 16 



75% flies July 19 July 19 



Last fly August 7 August 3 



The number of flies emerging equaled 34.6 percent of the total, an increase of 

 13 percent over the emergence in 1937 and slightly more than that of the pre- 

 vious year. 



Following the hurricane, nmch of the fruit remained on the ground long enough 

 to allow the maggots to reach full development and enter the soil for pupation. 

 This in all probability will lead to a great increase in the emergence of flies in 

 1939 with a correspondingly greater danger to next year's crop, and threatens to 

 place apple maggot once more in the forefront of orchard pests. 



Biology and Control of the Apple Leaf Curling Midge. (VV. D. Whitcomb, 

 Waltham.) In 1938, the area known to be infested by the apple leaf-curling midge 

 was extended nearly to the center of the Nashoba fruit belt of Middlesex and 

 Worcester Counties when this insect was found for the first time at Groton, near 

 Ayer; Littleton (near Lake Nagog); Littleton Common, North Littleton, Con- 

 cord, and Lexington. Also, an apparently isolated infestation at Sanford and 

 Alfred, Maine, was extended to North Berwick, Maine. All of these newly in- 

 fested localities are in a southwesterly direction from previously known infesta- 

 tions, indicating that favorable air currents during the emergence period of first 

 brood flies were responsible for this dispersion. 



The emergence of first brood flies extended from May 24 to June 17 with a 

 maximum on May 31. Rolled leaves infested with midge maggots were abundant 

 from May 31 to June 10, and the maggots migrated to the bark and soil in large 

 numbers from June 14 to 28. Eggs and flies were again abundant July 1 to 15 

 and all available new growth was rolled by July 18 when the second brood of 

 maggots began to migrate. Heavy rains from July 18 to 24 caused many maggots 

 to leave the rolled leaves prematurely, and after August 1 there was considerable 

 overlapping of generations. A small third generation of flies emerged in late 

 August and larvae were migrating from infested leaves as late as September 16. 



In the laboratory only 12 percent of the maggots which were overwintered in 

 cages emerged as flies. Of the first generation maggots which were collected 

 before July 19, over 95 percent transformed to flies; and 48 percent of the second 

 generation maggots maturing from July 19 to August 9 transformed; while only 

 7 percent of those maturing from August 19 to 26 emerged as flies. The length 

 of time required for mature maggots to change to adult flies averaged 21 days 

 in June, 17 days in July, and 24 days in August. 



When flies emerging July 6 to 9 were dissected, an average of 127 eggs per 

 female was found in 1-day-old flies, and 139.9 eggs in flies 2 days old. The greatest 

 number of eggs found per female was 231. 



