#mesostigmata

(Sources - 1, 2, 3, 4)

Order: Mesostigmata

Common Name: no common name

Superfamilies: 25 - Arctacaroidea, Ascoidea, Dermanyssoidea, Eviphidoidea, Phytoseioidea, Rhodacaroidea, Veigaioidea, Epicrioidea, Heatherelloidea, Zerconoidea, Parasitoidea, Diarthrophalloidea, Microgynioidea, Thinozerconoidea, Uropodoidea, Heterozerconoidea, Sejoidea, Aenictequoidea, Antennophoroidea, Celaenopsoidea, Fedrizzioidea, Megisthanoidea, Paramegistoidea, Parantennuloidea, and Cercomegistoidea

(There are around 130 families, so we’re counting superfamilies for this one)

Families without a superfamily: Dithinozerconidae (Dithinozercon halberti)

Species without a family: Meliponopus palpifer

Anatomy: single pair of spiracles positioned laterally on the body; three-segmented chelicerae; fused cephalothorax and abdomen; larvae have six legs while adults have eight

Diet: varies widely between species; some are parasitic, some are free-living predators of smaller invertebrates or their eggs, some eat pollen and nectar, some eat fungus, and some eat dead and decaying organic matter

Habitat: worldwide in terrestrial and freshwater habitats

Evolved in: Late Cretaceous

(source)

Propaganda under the cut:

meet Androlaelaps schaeferi, the hissing cockroach mite. when Gromphadorhina spp. were brought into captivity decades ago, their commensal mites came with them. the mites amble around the roach’s body, living off of food scraps and other debris, which actually helps keep their host healthy and clean.

when their ride is disturbed, the little passengers rush to a safe nook, often in the “neck” region where they’re well protected. even when their host dies, the mites are hesitant to leave the only home they’ve known.

when observing hissing cockroaches, you might have noticed a few brown specks scrambling over their backs or gathered in the seams of their exoskeleton. they are Androlaelaps schaeferi, a species of mite that lives its whole lifespan onboard a giant cockroach host! the commensal A. schaeferi isn’t a parasite, though, and takes its meals from its hosts’ own. if the mite’s mooching helps clean where the roach itself can’t, the relationship might even be considered mutualism, where both species benefit.

on the white of a freshly molted roach, the mites are particularly conspicuous, and even the pale juveniles stand out.