TEMPORAL CHANGES IN THE COMPOSITION OF THE OVERWINTERING LARVAL POPULATION OF THE MEDITERRANEAN FRUIT-FLY (DIPTERA, TEPHRITIDAE) IN NORTHERN GREECE

The temporal changes in the composition of different instars of Medite rranean fruit fly, Ceratitis capitata (Wiedemann), was studied in Thes saloniki, northern Greece, an area located within the European norther n limits of the fly's distribution. Field infested 'Golden Delicious' apples and apples of an unidentified local variety, were collected in autumn 1994, maintained outdoors during the winter of 1994-1995, and r egularly monitored for immature stages of Mediterranean fruit ny. No e ggs were found alive after the end of November. High incidences of 3rd instars inside fruits, and of fully grown larvae emerging from fruits to pupate, occurred in December-January. In both varieties, mortality and the emergence of the fully grown larvae from fruits reduced the n umber of living larvae per fruit from approximate to 5 at the end of N ovember to <1.3 at the end of December and to <0.3 by March. A low per centage (3.1 and 4.4% for the Golden Delicious and local-variety apple s, respectively) of Ist instars remained inside the fruits without mol ting until early March. Second instars were found in high numbers (20- 70% of the larval population) from November to March. The results sugg est that larvae that molted to the 3rd instar during lute autumn to wi nter pupate and die, but 1st and 2nd instars survive. They are thus th e main overwintering stage of C. capitata in northern Greece, yielding small adult populations in the spring. The importance of slow larval growth for successful overwintering is discussed.