DIAPAUSE DEVELOPMENT OF THE PEAR PSYLLA, CACOPSYLLA-PYRI (L) UNDER NATURAL CONDITIONS

In the Avignon area, the winter-form of the pear psylla, Cacopsylla py ri (L.), appears during the first 10 days of September, Adults continu e to emerge throughout the winter until January and even later. The se x-ratio is at first high, stabilizes at about I and then decreases in mid-January with the precocious mortality of males. Throughout winter, immature ovaries of winter-form females undergo a slow but constant d evelopment. Diapause does not prolong any particular ovarian stage and its completion seems to occur at any stage. The mating process is not strictly linked with the completion of diapause of winter-form female s. However, the latter do not mate with males of the summer-form which are still present in autumn.