Mouthparts of Hexapods
The hexapods are trignathan, that is to say they present three pairs of buccal appendages, each one of them situated in the corresponding cephalic segment: a pair of mandibles (mandibular segment), a first pair of maxillae (maxillary segment), and a second pair of maxillae that fused, form the labium (labial segment).
Recently, certain authors affirm that the classic point of view, according to which the true capacity of “biting” by the Dicondylia [Thysanura (Zygentoma) plus Pterygota] is functionally correlated to the acquisition of dicondylic mandibles, cannot be maintained, taking into account that the capacity of “biting” transversely is a trait characteristic of the hexapods. Therefore, the division of the mandibles into mono- and dicondylic is not fitting (Koch 2001); because of this, and owing to the great variability existing in the hexapods, this author prefers to treat separately the mandibles of each one of the large groups: Collembola, Protura, Diplura, Archaeognatha,...
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