Entognathous

Definition

Having mouthparts that are withdrawn into a pocket or groove of the head capsule and thus not visible externally; describing the condition in which the mandibles and maxillae are enclosed within the head, with only the distal tips of the labium exposed. This contrasts with ectognathous (exognathous) mouthparts, which are external and visible, as in true insects.

Etymology

Greek entos (within) + gnathos (jaw)

Example

Springtails (Collembola), proturans, and diplurans possess entognathous mouthparts, a diagnostic feature that historically united these groups as the class Entognatha separate from the ectognathous insects.

Related Terms

• Ectognathous
• Entognatha
• Hexapoda
• mandible
• maxilla
• labium
• Ametabolous

Usage Notes

Used primarily in hexapod morphology to distinguish the three entognathous orders (Collembola, Diplura, Protura) from ectognathous insects. The term describes a structural condition, not a taxonomic rank; the group once called 'Entognatha' is now considered paraphyletic. Specialists may use 'endognathous' as an occasional variant, though 'entognathous' is standard.