Where Do Apple Maggot Flies Find Food in 

 Nature? 



Jorge Hendrichs and Ronald Prokopy 



Department of Entomology, University of Massachusetts 



To manage insect pests effectively, we need to un- 

 derstand as much as possible about how they acquire 

 resources of food, mates, and egglaying sites. Over the 

 past decade or so, we have gained substantial insight 

 into how apple maggot flies search for mates and 

 egglaying sites. But until recently, neither we nor 

 anyone else has examined in a systematic fashion the 

 way the flies acquire food. In this article, we report on 

 the kinds of plants upon which apple maggot flies find 

 food in nature, and the types of food most frequently 

 eaten. In the 4 succeeding articles, we discuss how the 

 flies are able to detect the presence of food from a 

 distance, how flies search for food on leaf surfaces, the 

 kinds of food that support fly reproduction, and the 

 frequency with which the flies need to feed to attain the 

 greatest number of eggs. Information of this kind is 

 important not only in furthering our understanding of 

 fly behavior but also can be used in designing new 

 behavioral approaches to fly control. 



Methods Used 



In 1987, we conducted a quantitative assessment of 

 fly feeding activities in nature over time and space, and 

 identified feeding sites on host and non-host plants. 

 Observations were made in an abandoned apple or- 

 chard (mainly Early Mcintosh), in Amherst, Massa- 

 chusetts. Studies began in early summer when flies 

 first emerged from overwintering pupae, and contin- 

 ued through the entire period of a single fly generation, 

 for a total of over 300 observation hours. Flies were ob- 

 served systematically in three separate areas of the 

 orchard. Each of these areas included a fruiting apple 

 tree, a non-fruiting apple tree, and a transect through 

 the surrounding non-host vegetation. Equal observa- 

 tion time from 7AM to 6PM was allocated to each type 

 of tree and area. 



Results 



Results indicate that after fly emergence and for 

 approximately 7 days thereafter (corresponding to the 

 sexual maturation period), foraging for food is appar- 

 ently the predominant type of fly activity. At dawn, flies 

 of both sexes were at rest in upper, sunlit parts of tree 



canopies. It was here that they began feeding. As the 

 temperature increased, they moved progressively to 

 lower, more shaded positions. 



During the sexual maturation period (i.e., the first 

 week), flies were found mostly on non-fruiting host 

 trees and surrounding non-host vegetation. After this 

 first week period, fly presence shifted markedly to 

 fruiting host trees (Table 1), where matings and op- 

 positions take place on the fruit. The average number 

 of feeding events per observed fly decreased gradually 

 over time: 0. 16, 0. 14, 0. 12 and 0.12 for the first, second, 

 third, and fourth weeks of observation, respectively. 

 Each week, the percentage of flies observed feeding was 



Table 1. Total numbers of adult apple maggot 

 flies observed over 4 weeks (early July to early 

 August) on fruiting apple trees and on other 

 vegetation (non-fruiting host trees and sur- 

 rounding non-host vegetation) in an abandoned 

 apple orchard. 



Percent of 

 individuals present on 



Total number Fruiting Other 



Week observed host trees vegetation 



greater on non-fruiting host trees and surrounding 

 vegetation than on fruiting host trees (Table 2). 



Although as flies matured they spent increasing 

 amounts of time on host fruit for mating and oviposi- 

 tion, foliage remained the most common apple maggot 

 fly feeding site, followed by feeding on fruit surfaces or 

 wounds (Table 3). Flies spent considerable time mov- 

 ing from leaf to leaf, often dabbing their mouthparts on 

 apparently diffuse (i.e., non-observable) food resources 

 on upper leaf surfaces. The identity of these diffuse 

 resources remains to be determined (the fourth article 

 in this series gives further information on this subject). 



Fruit Notes, Summer, 1990 



