Key to female instars of Pseudochermes betula .

1 Legs present; antennae with 6 segments................................................ first-instar nymph (Fig. 1)

- Fore and middle legs absent, hind legs replaced by pore plates; antennae with 3 segments............................ 2

2 Vulva present; body circular-oval; thoracic dorsum with tubular ducts on medial area; anal ring surrounded by a nearly circular sclerotized plate............................................................................. -adult female

- Vulva absent; body oval; thoracic dorsum without tubular ducts on medial area; anal ring surrounded by an inverted U-shaped sclerotized plate................................................................. second-instar female (Fig. 3)