Two species of these freshwater animals are found in Central Europe, Apus cancriformis and Apus productus, the latter also lives here. They can be recognized by the shape of the tail flap, which in the first species is very short and notched. Behind the shield-shaped shell, which covers the body of these animals at the back, protrudes only the long hindquarters, the last segment of which bears two long tail threads. The front part of the dorsal shield shows the two almost merging eyes. There are 30 to 40 pairs of limbs; the eleventh forms 2 brood bags for the female storage of the eggs. On the back, only the 3 whip-shaped appendages of the first pair of legs are visible. The anterior blades are small, 2-membered, filamentous, the posterior only present in the larva state. The Gill Paws live in small puddles and other stagnant water; they die when their abode dries up. The eggs, which remain in the solidified mud, retain their development capability for a very long time.
[As translated online]