flies might inhabit largely the perimeter trees because 

 of their need to move back and forth to the surrounding 

 vegetation regularly to obtain food. This movement 

 could increase many-fold the probability of capturing 

 flies on odor-baited interception traps placed on pe- 

 rimeter trees before flies penetrated into the orchard 

 interior. 



Finally, if orchards were consistently scarce in 

 natural fly food, the effectiveness of perimeter inter- 

 ception traps (currently baited with synthetic apple 



odor) might be enhanced by the addition of synthetic 

 food odors. 



Acknowledgements 



We thank David Eagle and Maryam Masahayekhi 

 for their help during various aspects of these studies. 

 This work was supported by the Science and Education 

 Administration of the USDA under grant 8700564 

 from the Competitive Grants Office, and by the Massa- 

 chusetts Agricultural Experiment Station Project 604. 



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How Do Apple Maggot Flies Detect the 

 Presence of Distant Food? 



Jorge Hendrichs, Martha Hendrichs, Joshua Prokopy, and Ronald 

 Prokopy 



Department of Entomology, University of Massachusetts 



Brian Fletcher 



CSIRO, Canberra, Australia 



Our field observations, described in the first article 

 in this series, showed that in the absence of abundant 

 food resources on fruiting host trees, apple maggot fly 

 females leave hosts (even after the onset of egglaying) 

 to forage in the surroundings. We hypothesized that 

 odors from concentrated or high quality food sources 

 may direct this searching behavior. 



For years there has been no agreement on the 

 question of whether apple maggot flies respond to 

 commercial food baits as other fruit flies do, although it 

 is known that apple maggot flies do respond to ammo- 

 nia, a typical volatile product resulting from the bacte- 

 rial breakdown of food baits and other protein sources. 

 Based on these facts and our findings from the field, the 

 following 3 tests were carried out. 



Effect of Age and Protein Deprivation 



The objective in our first test was to determine the 

 effect of fly age and protein deprivation on the response 

 of apple maggot flies to ammonia volatiles. We released 

 flies of different feeding status, age, and sex in the 



center of a patch of 25 potted, non-fruiting hawthorn 

 trees in an open field at the Horticultural Resesarch 

 Center, Belchertown, MA. At the outer edge of this 

 patch and at a distance of 4 meters from the release 

 point, we placed (in alternating positions) 8 sticky- 

 covered 250 ml plastic vials filled with either a 0.1 

 molar solution of ammonium bicarbonate or water 

 (vials were 3 meters from each other). Fly capture on 

 outer surfaces of the vials was measured 30 minutes, 2 

 hours, and 24 hours after each release. The containers 

 were rotated every trial. 



Results in Table 1 show an important effect of 

 feeding status and sex, and to a smaller degree age, on 

 fly response to ammonia. Protein-deprived flies, at all 

 ages, were much more responsive to ammonia than 

 flies having fed recently on yeast. Under all situations, 

 females were much more responsive to ammonia than 

 males. Although protein-deprived females of all ages 

 responded to ammonia, the highest response occurred 

 in the latter part of the sexual maturation period (when 

 flies were 8 to 10 days old). Most of the fly captures 

 occurred in the first 30 minutes to 2 hours after release. 



Fruit Notes, Summer, 1990 



