7.3.2. Class and order Collembola (springtails)
Collembolans are minute to small and soft bodied, often with rudimentary eyes or ocelli. The antennae are four- to six-segmented. The mouthparts are entognathous, consisting predominantly of elongate maxillae and mandibles enclosed by lateral folds of head, and lacking maxillary and labial palps. The legs are four-segmented. The abdomen is six-segmented with a sucker-like ventral tube or collophore, a retaining hook and a furcula (forked jumping organ) on segments 1, 3, and 4, respectively. A gonopore is present on segment 5, the anus on segment 6. Cerci are absent. Larval development is epimorphic, that is with segment number constant through development. Certain controversial studies suggest that Collembola may have a different evolutionary origin to the rest of the Hexapoda (see Box 7.1). If Collembola do belong to the Hexapoda, then they form either the sister group to Protura comprising the clade Ellipura or alone form the sister to Diplura + Insecta. (See also Box 9.2)
