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

In a preceding systematic study in an apple orchard and its surroundings, we identified several natural substances upon which apple maggot flies, 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 fecundity. Tests were carried out in small laboratory cages and in large field cages containing potted host trees. Results indicate that fly longevity can be sustained by carbohydrate obtained in the form of leachate on surfaces of host foliage. This explains the extensive ''grazing'' behavior of flies on nonvisible substances on host plant surfaces devoid of honeydew. Egg development, however, was not sustained by host foliage leachate. Bird droppings, aphid honeydew, and to a lesser extent hawthorn fruit leachate, contributed to moderate fly fecundity, whereas 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 nutritional ecology are discussed, including the development of improved fruit fly attractants based on the identification of volatiles from natural nitrogenous sources such as bird droppings or insect honeydews.