Скачать или смотреть Earwig Forficula auricularia and its mite Histiostoma polypori

The common earwig Forficula auricularia is a representative of the insect clade Dermaptera. The phylogenetic systematic indicates a sistergroup-relation between Dermaptera (earwigs) and Dictyoptera (termites and cockroaches (both: Blattodea) and mantids).

Forficula auricularia is a hemimetabolic insect, being omnivorous and feeding on plant tissue and on other arthropods, such as aphids and their eggs.

This earwig species shows a social behavior in the sense of a well developed maternal care. The female creates a brood-chamber, where she actively cares for her eggs as well as for the younger nymphs, for example by defending them against predators.

After all instars and their mother have left the nest completely, an aggregation behavior remains for a while. They then aggregate at different suitable locations during the day, for example under the bark of dead trees. The earwigs, visible in this film, where found under such conditions. Older nymphs and an adult female aggregated under a dead piece of wood. During the shooting period of this film, some nymphs had developed into adults.

Forficula auricularia originally was distributed in Europe, but at the beginning of the 20th century, it had arrived to North America as a neozoic organism.

Interestingly, Forficula auricularia is known to carry regularly a mite of the Astigmatina (Astigmata, Histiostomatidae): Histiostoma polypori.

According to some researchers and my own scientific/ acarological studies, the phoretic dispersal stage of this mite (the phoretic deutonymph) attaches once in its life a juvenile earwig and remains on it until the earwig molts into an adult. For this purpose, the mite needs to be able to switch from one earwig stage to the following one during or shortly after the earwigs molting.

My own research indicated ( Wirth S.: Necromenic life style of Histiostoma polypori (Acari, Histiostomatidae). In: Experimental and Applied Acarology. 2009; 49: 317-327, PMID 19697142, doi:10.1007/s10493-009-9295-6) that the mite deutonymphs on an adult earwig female leave their earwig, when she is breeding inside her nest. There the mites develop to adults, feeding on bacteria, which grow on decaying material, mostly on cadavers of died earwig nymphs. The phoretic deutonymphs of the new generation then attach to surviving earwig nymphs, still inside their nest.

Such life cycle correlations of different organisms might be a result of coevolution. In this context, it needed to be proved that also the earwig has adaptations to deal with its mite. A closer research is still necessary.

In case the mite indeed is carried to earwig nests only to develop on earwig cadavers there, this might be seen as a life-style, different from a "normal" phoresy (transport via insect to a new habitat). That's why I used the term necromeny in my scientific paper.

Histiostoma polypori seems to be specifically adapted to Forficula auricularia. But other mite species of the Histiostomatidae were discovered to be associated with tropical earwigs (e.g. Kazumi Tagami and Bruce Halliday, 2013. Australian Journal of Entomology, Volume 52, Issue 3, pages 218–226).

I own the copyrights for the whole film, including earwig and mite-footage, SEM picures (scanning electron microscopy,) drawings and sound.