Dorsal shield - number and form

Dorsal Shield - number and form

Many early derivative lineages of Mesostigmata have adults covered dorsally by a complex of shields of various sizes, a condition that is typical of immature stages. This 'fragmentation' of dorsal shields also occurs in some derived lineages.
In many other groups the dorsum is covered by two more or less equal shields, an anterior podonotal and a posterior opisthonotal shield. Rarely the anterior shield may have deep notches or lateral incisions.
In many groups of Monogynapsida the dorsum of the adult female is covered by a single, entire holodorsal shield, typically oval to subrectangular in shape, or sometimes tapering posteriorly an resembling an inverted teardrop or spear point.
Rarely the dorsal shield may be truncated posteriorly, leaving most of the opisthosoma uncovered.
Some groups have relatively shallow to deep incisions at the level where the podonotal and opisthonotal shields would fuse. In a few mites, e.g. some Phytoseiidae, shallow notches occur in the podonotal region.