periods. 



The results (Table 1) showed that females that had 

 continuous access to sugar and yeast laid nearly 70 

 times as many eggs as adults that had continuous 

 access to sugar but no access to yeast, and 4 to 12 times 

 as many eggs as adults that had continuous access to 

 sugar but access to yeast only for a single 4- or 8-day pe- 

 riod. The results suggest that access to yeast might be 

 particularly important during the first week of life but 

 that even after reproductive maturity is attained by the 

 end of the first week or so, females still require frequent 

 protein intake to sustain high reproduction. 



In our last test, we were interested in denning 

 more precisely just how much time can elapse between 

 protein meals before fly fecundity is affected. We al- 

 lowed flies free access to yeast either every day or every 

 second, fourth, eighth, or twelfth day. 



The results (Table 2) show that females need to 

 ingest protein at least every fourth day to maintain full 

 egglaying capability. Successively fewer eggs per day 



Table 2. Egglaying capability of females having 

 free access, at different intervals of time, to pro- 

 tein (in the form of enzymaticyeasthydrolysate). 

 Flies in all treatments were provided with a 

 continuous supply of carbohydrate (in the form 

 of sucrose) and water. There were 6 replicates 

 (cages) per treatment, each with 6 males and 6 

 females. 



were laid when females ingested protein every fourth, 

 eighth, or twelfth day. 



Conclusions 



Our combined laboratory studies show that both 

 sexes of apple maggot flies need to feed and drink at 

 least every other day or every third day just to be able 

 to move about and survive. They also indicate that 

 while continuous access to carbohydrate in the form of 

 sucrose is sufficient to permit long life and reasonable 

 movement, females need to acquire protein at least 

 every other day to maintain a high level of reproduc- 

 tion. In nature, it is quite likely that under many con- 

 ditions females do not have continuous access to such 

 high quality protein as we offered them in our labora- 

 tory cages. Therefore, in nature it is probable that most 

 females take in smaller meals of lower quality protein 

 than females did in our laboratory cages and that they 

 need to do so on an every-day basis to sustain high 

 fecundity. This probably explains why we observed so 

 many apple maggot females, even late in the season, 

 away from fruiting host trees and feeding on non-host 

 plants. Thus, females in nature may not be prone to 

 spend long periods in orchards having little supply of 

 insect honeydew, bird droppings, or other protein 

 sources. To reiterate what we suggested in the first 

 article in this series, protein-seeking females may be 

 quite responsive to the odor of chemicals emitted from 

 protein sources (for example, ammonia). Such chemi- 

 cals could be useful, in addition to synthetic fruit odor, 

 in attracting females to interception traps on perimeter 

 apple trees. 



Acknowledgements 



We thank Maryam Mashayheki and Patti Powers 

 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. 



Fruit Notes, Summer, 1990 



13 



