Thirty- to 40-day-old embryos from stick insect eggs were used for the preparation of metaphase chromosomes—initial preliminary work (our own unpublished data) indicated that eggs of this age were best suited for chromosome preparations. The embryos were dissected out of the eggs and placed in a 0.9% sodium citrate solution at room temperature. For 20–30 min they were fixed in a cold methanol:glacial acetic acid mixture (3:1). Fixed embryos were macerated in a drop of 60% acetic acid on slides and air-dried . The per-species available metaphases for the present study are listed in Table 1 (~2 metaphases per embryo; in M. extradentata the amount was doubled).