How Often Do Apple Maggot Flies 

 Need to Eat? 



Jorge Hendrichs, Sylvia Cooley, and Ronald Prokopy 



Department of Entomology, University of Massachusetts 



Our findings set forth in the first article in this 

 series revealed that adult apple maggot flies, whether 

 immature or sexually mature, may leave fruiting host 

 trees frequently in search of food on other nearby 

 vegetation. This finding implies that the flies may need 

 to eat rather often. In this article, we report some 

 results of laboratory tests aimed at determining just 

 how frequently apple maggot flies do in fact require 

 food to maintain a high rate of reproduction. 



Unlike many other types of flies that lay large 

 batches of eggs in cycles, apple maggot females typi- 

 cally lay a few eggs every day, which necessitates a 

 regular supply of protein. Males, on the other hand, 

 have a very low (if any) protein requirement for repro- 

 duction. Both sexes need regular intake of water and 

 carbohydrates simply to survive. 



Tests of Food and Water Deprivation 



The first question we posed was: what are the nu- 

 tritious reserves that the flies carry with them at emer- 

 gence that allow them to survive until they come upon 

 their first food and water? To answer this question, we 

 carried out an experiment to observe the effect of size of 

 pupae and pupal reserves on fly longevity after emer- 

 gence. Each of 480 pupae, belonging to three selected 

 size categories, was weighed and kept individually. 

 Upon emergence, each fly was placed immediately into 

 one of four treatments: (a) no food, no water; (b) food 

 (yeast and sucrose), no water; (c) no food, water; and 

 (d) food, water. 



Average longevity of flies was about 2 days when 

 they had no food and no water, 3 days when they had 

 food but no water, 4 days when they had no food but 

 water, and 50 days when they had both food and water. 

 Within each of the four treatments, survival decreased 

 with decreasing fly weight. Smaller females were more 

 affected than smaller males. Apple maggot flies are 

 nearly motionless during the first hours after emer- 

 gence, when their wings are hardening. During much 

 of the latter part of the deprivation period in our study, 

 they appeared too weak to forage and to evade preda- 

 tors. Therefore, the time during which emerging flies 

 are able to forage effectively for their first food and 

 water may be restricted to no more than a day or so. 



Next, we deprived flies that previously had free 

 access to food and water for 8 to 16 days prior to depri- 

 vation. At the start of deprivation, the females had at 

 least a partially developed egg load, with some stored 

 food reserves in the crop. Even in this case, we found 

 that flies could survive without food only for a little 

 longer (for 3 to 5 days) than they could when they were 

 deprived immediately after emergence. Again flies 

 appeared too weak to forage effectively for food for 

 much of the last part of the deprivation period. Appar- 

 ently, food reserves stored in the crop and elsewhere 

 are exhausted rapidly, even when flies have had plenty 

 to eat for the preceding week or two. 



Tests of Periodicity of Feeding 



Given the above findings, we then asked what is 

 the importance of feeding during the one-week period 

 of fly maturation versus the importance of feeding after 

 the onset of egglaying? A laboratory test was carried 

 out to determine how critical the availability of protein 

 (in the form of yeast) was during these 2 different 



Table 1 . Egglaying capability of apple maggot fly 

 females having free access, for varying periods of 

 time, to protein (in the form of enzymatic yeast 

 hydrolysate). Flies in all treatments were pro- 

 vided with a continuous supply of carbohydrate 

 (in the form of dry sucrose) and water. There 

 were 6 replicates (cages) per treatment, each 

 with 6 males and 6 females. 



Days during life with 

 access to yeast 



Lifetime number of eggs 



laid per female per day 



in artificial fruit 



No days 

 Days 1 - 4 

 Days 4 - 8 

 Days 1-8 

 Days 8-11 

 Days 11-15 

 Days 1-42 



0.04 

 0.44 

 0.66 

 0.60 

 0.22 

 0.42 

 2.61 



12 



Fruit Notes, Summer, 1990 



