Some Observations On the Number of Larval Instars of the Oriental Peach Moth, Laspeyresia Molesta Busck

Abstract

By applying Dyar's ideas that the width of the head-capsule of a lepidopterous larva is more or less constant for any instar of a given species and that successive e larval instars of a given species show. a more or less regular geometric progression in the growth of the head-capsules, oriental peach-moth larvae are found to have four or five instars. The number of larval instars produced is correlated with the rate of larval growth. As a rule rapid growth produces four instars and slow growth five instars. Rapidity of larval growth is dependent upon at least two factors, temperature and food. High summer temperatures produce rapid growth while low temperatures, such as occur in the spring and fall, produce slow growth. Larvae develop somewhat faster in peaches than in apples under insectary conditions. The rate of development of individual larvae in a given food varies Considerably.