OOGENESIS IN THE ADULT OF THE EUROPEAN EARWIG FORFICULA AURICULARIA (DERMAPTERA: FORFICULIDAE)

Abstract

AbstractOogenesis and associated ovarian development were studied from the onset of adult eclosion to oviposition in the European earwig, Forficula auricularia L., by examining histological sections of ovarioles and whole mounts of ovaries. Each pair of ovaries contains a mean of 85.4 ovarioles. Chronologically, oogenesis has been divided into four phases, adult emergence, previtellogenesis, vitellogenesis, and choriogenesis, each described here in detail. The mean size of the basal follicle increases from 15 μm at time of adult emergence to 0.9 mm at time of choriogenesis, and the oocyte to trophocyte ratio increases from 1.0 to 4, with a minimum of 0.5 at the onset of previtellogenesis. The oocyte to trophocyte ratio of 0.7 marks the onset of vitellogenesis, which lasts about three times (60 days) as long as previtellogenesis. The extended vitellogenesis is still under way when females bury themselves in the ground, in October, in the Montréal area.