SPRINGTAIL  , the

common name of a group of small insects, so named from the presence of a pair of tail-like appendages at the end of the abdomen, which acts as a spring . When the insect is undisturbed these appendages are turned forwards and held in position by a catch beneath the abdomen; but in case of alarm they are kicked forcibly downwards and back-wards, jerking the body into the air . This action may be rapidly repeated until a place of safety is reached . These insects usually live under fallen leaves, stones or the bark of trees, and sometimes occur in such quantities as to resemble patches of powder or dust . One species (Podura aquatica) may be seen floating in this way in masses upon the surface of standing water . Another (Achorutes socialis) may sometimes be found in abundance in the snow . Zoologically the springtails belong to the sub-order Collembola of the order Aptera (q.v.) .