Necromenic life style of Histiostoma polypori (Acari: Histiostomatidae).

Histiostoma polypori (Histiostomatidae, Astigmata) is associated with the earwig Forficula auricularia, which has an interesting brood behavior: the adult earwig female cares for her eggs and stays with the N2 and N3 nymphs in the nest. Deutonymphs of H. polypori only leave the female earwig to develop on dead earwig N2 and N3 nymphs. The newly molted deutonymphs attach to live earwig N3 nymphs. The earwig's cleaning behavior displaces the deutonymphs to the exuvial suture, around the area between cephalon and prothorax. From there, deutonymphs switch from one earwig stage to the following, always occupying that region. Histiostoma polypori obviously has a necromenic life style, that is, it ascends a carrier organism and develops on the carrier's cadavers. Necromeny within the Histiostomatidae presumably derived at least twice convergently from phoretic transport.