Beintastler ( Acerentomon sp.)
Mute - Traun Rock, 1891
As Sackkiefler ( Entognatha ) the combined group is called from Beintastlern, double tails and springtails within the Hexapod. The reason for this taxon - education is a mouth pocket in which the mouthparts are and which is present in all three groups. Made the bag is by lateral folds of the head capsule, which is fused to the back of the lower lip ( labium ). Thus, the mandibles and maxillae that are drawn into the head capsule and usually modified into piercing and Spatelwerkzeugen.
The Sackkiefler are compared with the Freikieflern ( Ectognatha ) as a sister group. Within the Entognatha springtails and Beintastler be summarized as Ellipura and compared with the double tails. The main argument for this group in addition to various other reduction features, the lack of abdomen attachments and the fusion of the lower leg (tibia) with the foot ( tarsus ) are given to the tibiotarsus.
The Sackkiefler are not without controversy as a taxon, especially the position of the double tails within the Hexapod is not yet fully understood. Although the most common classification of double tails takes place within the Sackkiefler, there is at least one alternative hypothesis ( Kukalová - Peck, 1987). After this, the Diplura could itself be regarded as a sister group of insects, while a common taxon named Ellipura could in turn be viewed as a sister group of these two groups. As a causative feature here the evolutionarily different number of leg sections is considered, which are fused with the abdominal plates of the abdomen. This feature, and thus the hypothesis, however, are very controversial. If true, this hypothesis, the Sackkiefler must be resolved as a taxon.