Poecilochirus

At least eight species of the genus are carried from one food source to another by beetles of multiple genera in the family Silphidae, most notably burying beetles. The mite deutonymphs sit on the adult beetles, typically between the coxae or under the elytrons. The beetles breed on carrion, which some species bury. Once arrived on carrion, the mites leave the beetles, feed on the carrion, and develop into adults.^[8] The entire life cycle of the mites takes place on the carrion, and the young mites later leave again with the beetles.^[4]

The probably best studied species are from the Poecilochirus carabi species complex that consists of at least two species (P. carabi and P. necrophori).^[3][4][9] In Europe, the two mite species are specialized on two different species of burying beetles, Nicrophorus vespilloides and Nicrophorus vespillo. The mites can recognize their main host beetle species and can produce more offspring along their preferred host beetle.^[4][9] Similarly, two genetic lines of Poecilochirus carabi mites have been reported from North America, which specialize on different sets of Nicrophorus hosts in some populations.^[10]

It is debated whether the mites harm the beetles or benefit them. Under certain conditions, the mites appear to protect the beetles' larvae or their food supply from fly larvae,^[11][12] but the presence of mites on beetle-tended carcasses also reduces male beetle life span and the number of beetle offspring.^{[13][14][9][15][8]}

There is no recent treatment of the genus Poecilochirus. Identification keys mostly rely on the extent of a dark band across the sternal shield, the size of the dorsal shields, the doral chaetotaxy (mainly the length of the setae), and appendices of the fixed digit of the chelicerae.^[2] The first description of all life stages was published by Neumann.^[16]

A study of the Poecilochirus carabi complex genetics ^[20] suggests that the species complex consists of many more than only two species (P. necrophori and P. carabi). The mites from Asia and America that would previously have been identified as P. carabi based on their morphology are from distinct genetic lineages. Data suggest that there may be 17 different P. carabi complex species that are not yet described. In addition, the mites that have been identified as P. subterraneus based on their morphology also likely belong to more than one species.