POPULATION FLUCTUATIONS OF ADULT MEDITERRANEAN FRUIT-FLIES (DIPTERA, TEPHRITIDAE) IN A MEDITERRANEAN HETEROGENEOUS AGRICULTURAL REGION

We investigated the regional population fluctuations of the Mediterran ean fruit fly, Ceratitis capitata (Wiedemann),in a Mediterranean setti ng located in the hills (700 m above sea level) of central Israel. The region is composed of commercial orchards, residential mixed-fruit ga rdens, and Mediterranean shrubs and forests. Adult C. capitata populat ion in the studied region was sampled weekly for 2 years (1994-1995) w ith Trimedlure traps spread as grids of different scales (between 74-1 30 traps). No flies were trapped during the winter and early spring mo nths. During the summer and fall, flies were caught sequentially in tr aps located on host trees (i.e., apple, fig, and mixed fruit-gardens w ith apricot, plum, and others) at varying times of maturation. Flies f irst appeared in 'Granny Smith' apple orchards (May-June), which are a lso the same places where the last adult flies were trapped during Dec ember. This fact points at the possibility that C. capitata overwinter s as larvae in these orchards on nondecaying apple fruits. Small numbe rs of flies were caught in traps located on nonhost trees-with the exc eption of English walnut, which showed large trapping numbers between May and August and which seems to be related to the availability of la rge amounts of aphid honeydew that probably served to replenish energy reserves of the overwintering populations. Traps on abandoned tig tre es, which have the apparent role for the expansion of the population i n the summer, caught large numbers of flies between August and Novembe r. We conclude that the perpetuation of C. capitata in this Mediterran ean setting reflects the ability of an overwintering population to rea lize its reproductive potential by exploiting the continuous successio n of oviposition hosts during the warmer months.