Phoretic Mites waiting on Ant Pupae
Greater numbers of pupae from a nest of the myrmecine ant Myrmica rudinodis are attached by phoretic mites, which wait for these pupae to hatch. They would then attach the newly developed ants to be carried around and dispersed this way. They this way had already occupied their later ants before, namely during their pupal stage, one could call this phenomen „pupa-guarding“. In my samples, I discovered two species of mites performing this pupa guarding behavior. Most abundant were deutonymphs of the mite Forcellinia wasmanni (Astigmata). But also individuals of a mite species of the Gamasina were repeatedly discovered sitting on pupae, where they were hiding between head, ventrum and limbs of the pupa. They even seemed to defend their pupae, when they felt disturbed, e.g. by my filming activities.
Ant pupa guarding by mitees, looking for a carrier for dispersal
These pupa guarding-findings concerning this ant and with these corresponding mite species might be new to science (so far I didn’t found literature indications) and thus need to be studied closer in the future in order to understand the whole context of behaviors. In the footage, two types of pupae are visible, pupae of the winged alates and those of workers. Mites generally prefered both, but especially the deutonymphs of Forcellinia wasmanni seemed to appear more often on the pupae of later workers. Most pupae had at least one deutonymph attached, rarely, there were found up to four individuals. This is different to what could be found on older workers. They on their ventral side can have 4-6 deutonymphs. Many workers seem to be covered with the deutonymphs, but I didn’t check more workers until now, so I can’t say, how many were without mites. It is unknown, how deutonymphs come to the pupae, whether they simply leave older workers for the pupa-guarding or whether they were waiting in the soil for the pupae to arrive (due to the brood caring activitoes of the ants).
Mite-Life inside an ant nest. Copyrights Stefan F. Wirth 2015/18
Astigmatid mite with a strict relationship to ants
The mite Forcellinia wasmanni is known to be strictly associated with ants (e.g. Türk & Türk 1957). It is clear that attaching young female alates would secure the dispersial of the mite into a new ant nest. It is not clear, which function the transport via ant workers can have. But Türk & Türk (1957) mention that the free living instars of Forcellinia wasmanni would feed on dead ants. Such a kind of microhabitat for the development is not unique in astigmatid mites. Some species within the Astigmata are known to have such preferences for decaying cadavers, but are then feeding on microorganisms, which grow on these (insect) cadavers. Ant workers might be ideal to carry mite deutonymphs to new cadavers, where they would leave and develop. Ants generally have a very well developed hygienic behavior. This guarantees the mites to get access to cadavers regularly. I do not know any other video footage, showing living deutonymphs attached to their carriers on such a magnification level as visible in this film. The original footage of these deutonymphs is much longer.
Morphology and behavior of the dislersal-instar, the so called „deutonymph“
The function of the proterosoma (dorsal shield of the forebody) is acting as a flexible structure, protecting the mouthpart-area (non-functional in deutonymphs) and the fore-legs, but being very motile and being easily pushed backwards (under the following hyterosoma-shield), when the mite lifts up from the surface of the ant pupa. I cannot state much more concerning the second mite, found on pupae, which is a species of the Gamasina. I discovered this phenomenon only on three of my pupae. Ant nests represent complex communities of organisms, to which fungae, other insects, mites and nematodes can belong. The samples visible in this film were collected in July 2015 on the German island Usedom inside a forest area between the villages Zinnowitz and Karlshagen. The ant nest was quite small. An ant hill was not visible.
Complexity of life in ant nests
The complexity of life within ant nests is a result of evolution. I am an enemy of creationistic movements, including all modern faces of creationism. Creationism stimulates carelessness und illiteracy in the believing people.
Berlin August 2015/ December 2018, copyrights Stefan F. Wirth