Meiosis I of Bittacus sinicus A diffuse diplotene with the condensed sex chromosome and decondensed bivalents B diplotene, showing the bivalents are held together only at exchange points (arrows) C diakinesis, showing the evident chiasmata (arrows) D bivalents assembling at the equatorial plate in metaphase I (polar view) E, F metaphase I in side view, showing the ring-shaped bivalents with two chiasmata and rod-shaped bivalent with one terminal chiasma (asterisk) G anaphase disjunction, showing the divided bivalents and the undivided sex chromosome H anaphase I, showing the chromosome number of B. sinicus is 2n = 15 I telophase I. Arrowheads show the sex chromosome. Scale bars: 10 μm.