CONTRIBUTION OF NATURAL FOOD SOURCES TO ADULT LONGEVITY AND FECUNDITYOF RHAGOLETIS-POMONELLA (DIPTERA, TEPHRITIDAE)

In a preceding systematic study in an apple orchard and its surroundin gs, we identified several natural substances upon which apple maggot f lies, Rhagoletis pomonella (Walsh), were observed to feed. The primary objective of this investigation was to assess the identified natural substances for their contribution to apple maggot fly longevity and fe cundity. Tests were carried out in small laboratory cages and in large field cages containing potted host trees. Results indicate that fly l ongevity can be sustained by carbohydrate obtained in the form of leac hate on surfaces of host foliage. This explains the extensive ''grazin g'' behavior of flies on nonvisible substances on host plant surfaces devoid of honeydew. Egg development, however, was not sustained by hos t foliage leachate. Bird droppings, aphid honeydew, and to a lesser ex tent hawthorn fruit leachate, contributed to moderate fly fecundity, w hereas preparations of leaf surface bacteria, pollen, insect frass and uric acid did not support significant egg development. Fecundity was greatest where flies were exposed to enzymatic yeast hydrolysate. Some practical implications of a better understanding of R. pomonella nutr itional ecology are discussed, including the development of improved f ruit fly attractants based on the identification of volatiles from nat ural nitrogenous sources such as bird droppings or insect honeydews.