Subcapitulum and Hypostome

Various features on the underside of the capitulum are diagnostic for some taxa of mites.  For example, the denticulate hypostome is present only in ticks (Ixodida) and a median subcapitular gutter is present only in Mesostigmata and Holothyrida.  Only some Endeostigmata and traditional Oribatida retain a labiogenial suture (i.e. are diarthric or stenarthric): Prostigmata are always anarthric.  Several lineages of Oribatida, Endeostigmata, and a few Prostigmata (Eriophyoidea, some larval water mites) have developed suctorial mouthparts, i.e. the hypostome is elongated and curled around the chelicerae (typically stylets) and presumably used to suck up fluids.