Abstract
Indotritia cf. heterotrichia, a box moss mite 800 μm in length, combines the abilities to curl up and to jump. Despite the lack of specialized legs and of extensor muscles in its knee joints, the backward leap is characterized by a short take-off time (ca. 0.5 ms). This is apparently facilitated by a catch mechanism made up of a small hook on each forefemur that hitches on the rim of the anterior shield of the body and maintains the forelegs in a flexed position during a prejump phase. While the animal is propelled backwards, its body simultaneously spins in a forward direction: it is supposed that, at take-off, the hindlegs initiate a forward rolling of the body, which is powered by internal hydraulic pressure, before the hook disengages from the shield rim and triggers a sudden backward impulse. The non-parabolic trajectory of the flight can be described with a model where the air resistance due to the spin (Magnus effect) and to the translatory motion is taken into account.