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Kategorie: Biologie

Mite Histiostoma palustre (Histiostomatidae, Astigmata), a mite species with two different male types

Current state of knowledge

Habitat and summary of general biology

I discovered the mite Histiostoma palustre in 2000 (and reared it at least until 2001) in the Berlin gravelpit area „Im Jagen 86“ at about 52°29’18.7″N 13°14’28.2″E and published the description in 2002 (2003). It is phoretically associated with at least two Hydrophilidae beetle species in bank mud (sapropel) around (in times of the sampling several) ponds. The phoretic juvenile instar deutonymph attaches its host insect to be carried that way to a new suitable habitat.

SEM photograph of ventral side of the deutonymph of Histiostoma palustre. © Stefan F. Wirth
SEM photograph of ventral side of Histiostoma palustre deutonymph as negative version, emphasizing single sicking structures and shapes of hind legs, © Stefan F Wirth

Phoretic hosts and attachment site

I in those times determined two host beetles as belonging to the genera Coelostoma and Cercyon. In laboratory host choice tests, in which deutonymphs in a culture had the choice between three different potential host species, there was a significant preference for those Hydrophilidae beetles, while another offered beetle species sympatrically living the same habitat was almost not at all attractive for the phoresy instar. But the choice test was performed as a smaller side project only and offered not more than a host tendency, as for example not a representative variety of insect species from the same natural field habitat of the mite was involved in these choice tests. But indications were at least clear enough that a host specificy (on a higher taxonomic level) of H. palustre can be stated. Mites preferred according to these tests a specific area for attachment on their hosts, which was the dorsal head area.

Two different male types and the difference between polymorphism und polyphenism

The mite showed under laboratory conditions a male diphenism with highly modified gripping organs or normal legs2. While the modified leg can appear on both sides or only on the left or the right side.

Polymorphism“ is used internationally as the overriding term for such a phenomenon. Here, following the teaching of my former research group at the FU Berlin, I distinguished between a purely genetically determined expression of distinctly deviating morphs and the determination of these morphs by the presence of certain environmental factors. In the latter case we are talking about polyphenism. Of course, genetics also play a certain role here additionally.

Studies with cultures grown at different temperatures suggested that males with modified legs 2 appeared significantly more frequently at higher temperatures than at lower temperatures.

Temperatures: 30-32 °C (measured in summer inside the culture dishes at room temperature) and 20°C (climate cabinet, temperature inside and outside the cultures almost equal). Experimental approaches and total numbers of males counted: 10 cultures with lower (don’t remember exactly) numbers of developing mite stages per each of the two different temperatures. n=237 males in total at low temperature, n=729 males in total at high temperature. The number of modified males grew significantly from 18% (20°C) to 45% (30°C), while normal males decreased significantly from 82% to 55%.

Therefore I called the mechanism for the formation of two morphs diphenism. These studies were also a besides project and the amount of data would need to be even bigger according to higher level statistical requirements.

SEM photos of a male morph with modified legs 2, © Stefan F Wirth
Detailed SEM view to a male with legs 2 on both sides modified into gripping organs, perspective almost from the front side. © Stefan F Wirth

About the function of the modified male legs

I could observe in the mite cultures in which H. palustre thrived very well on decomposing potato pieces at about 20°C room temperature that the modified legs of the heteromorphic males used as prehensile organs played a role in intraspecific competition for female mating partners. Here several males, with and without gripping organs, were usually wedged together in veritable clusters around female tritonymphs or adult females. This was because the fighting happened more or less in a slow motion speed with apparent longer lulls in between. During the fights, the legs of the opponents were seized with the prehensile organ and the competitor was slowly pulled away from the coveted female.

Less is known about which selective pressure would favor the morph with gripping organ

Males with normally developed legs were at least seemingly in my observations clearly at a disadvantage here, since their second legs in particular could be easily grasped and they were hardly capable of defense and counterattacks. Nevertheless, random counts at that time did not provide any clear indication that heteromorphic males were possibly found significantly more frequently in the final mating position. The same applies to expectations regarding an unequal sex ratio in favor of males. Instead, males and females appeared to be almost evenly distributed in random evaluations. Additionally males with modified legs on both sides and with only one modified leg on the right and the left were in randomly counted cultures seemingly equally distributed.

Still many questions unanswered about the biology of H. palustre

It was unfortunately not tested at all, whether females mated by heteromorphic males and those mated by homomorphic ones had different reproduction successes. In connection with this biologically highly interesting mite species, many questions about its life strategies could not be examined deep enough during times of my PhD thesis. There was no time for this, since my research at the time was geared towards systematic comparative studies of numerous species. Unfortunately, the species could so far not be found again in its habitat „Im Jagen 86“ – at least not by the means of substrate samplings with only accidental Hydrophilidae inside – until today so that further studies were not yet carried out. This seeming lack of the species‚ presence in its former habitat is probably due to ecological changes in this area, which originally had several ponds, from which now only one remained.

A normal leg 2 of H. palustre compared with a modified leg indicating homolog leg articles and corresponding setation.

What makes this male diphenism interesting from the evolutionary point of view

Two distinct morphs within the same sex of a species is the result of evolution. It does at first not matter, whether it is a dimorphism or a diphenism. A fundamental question, which cannot be answered at this time, is: does the trait of these two morphs indicate that the species is on the way to finally having exclusively only males with prehensile organs, and is the species even on the verge of becoming the to cross the species boundary into a new species? Or is the characteristic of two male types a permanently stabled character, because exactly this has strong selection advantage?

In this context, fossil finds of closely related species (in amber) would be of interest, but unfortunately these are not yet known. It would also be interesting to compare different populations of this species, which are also not yet available. It furthermore would be of interest to understand, what exactly the advantage of modified males versus non modified males might be. Is it possible that an advantage of the modified-legged males is simply that they copulate more frequently, although smaller datasets have not yet confirmed this? And/or do females mated by modified males produce significantly more offspring?

And in the special context of the knowledge at that time that it is a temperature-dependent diphenism, one could raise the question of whether the species „evolutionally prepared itself“ by developing two male forms to cope better with temperature fluctuations. In view of increasing global warming, this may be of general biological interest.

A similar species from Egypt

A publication about a species with modified legs 2 as in H. palustre

In a conference proceedings contribution Bishlawy, S. E. M. O., and S. F. M. Allam published an article containing the description of a species of Histiostomatidae, which the authors have named Histiostoma egypti ( Proc.2nd Inter.Conf.Ent.Soc.Egypt, vol. 1, pp. 407-420, 2007). This is worth of being mentioned here more detailed in context of a possible close relationship of these species or a convergent evolution. But due to the lack of systematic facts, a decision hypothesis is not yet made. I can just emphasize that one showed me photos of that species on a conference in Cairo (Egypt) in 2003, and my first and superficial interpretation was that it even is Histiostoma palustre.

I have not checked whether the species Histiostoma egypti has been accepted internationally as a new species and is therefore also listed in the Zoological Record, as this is not relevant to the considerations here. It is interesting that a similar species was discovered in Egypt, about which there are some biological observations.

However, I only have a text version without illustrations, which is online published like that and which is why I cannot assess this species systematically/taxonomically on a deeper level. The authors refer to a similarity of their species with Histiostoma palustre including a similar diphenism of the males. I, as I already mentioned above, remember confirming this resemblance at an acarological conference in Cairo in 2003, where the co-author showed me photos of the later H. egypti.

Association with laboratory cultures of entomopathogenic nematodes

According to the authors, the species entered the laboratory with entomopathogenic nematode substrate and is doing well in the nematode cultures. The mite species is called semiaquatic, which quickly dies off at lower humidity. According to the authors, the thriving of the mites is to the detriment of the nematodes, which can die as a result. In this context, the authors mention having observed that the heteromorphic male form appears more frequently when live nematodes are present, while the homomorphic form and also the phoretic deutonymphs predominate when previously present nematodes have died.

My general experiences with histiostomatid mites and free living (phoretic) nematodes

A connection between the development of different mite morphs and the presence or absence of living nematodes never became particularly obvious to me in my studies at the time on species with different male types. Therefore, I have never specifically investigated such a connection and can therefore judge the correctness of such a connection as neither improbable nor very probable.

I can confirm, however, that basically all Histiostomatidae species that I examined always appeared together with nematodes, which were usually free-living, microorganism-eating representatives of the Rhabditidae or Diplogastrinae, which are also phoretic and possibly even were spread by the same hosts as the mites.

In this context, I am aware of the phenomenon that nematodes and mites can either compete with each other for food or reduce each other, for example chemically. In any case, it can often be observed that after some time in a culture vessel in which both animal groups were initially numerous, only the mites or the nematodes thrived in large numbers.

General information about the feeding behavior in Histiostomatidae

According to my recent research, based on frame-by-frame videographic analysis and SEM studies, Histiostomatidae species use their filter-feeding mouthparts to feed on decomposing fungal material that is also bacteria-rich. It is highly probable that the fungi are brought by the mites themselves into their habitat, which seems to happen hyperphoretically via fungal spores. The mites probably also control the growth and partial death of the fungus themselves in the form of their fungicidal gland secretions. Specific studies about the feeding behavior of H. palustre do not exist on a more advanced level. Slides and numerous SEM shots might indicate the transport of spores, but I so far had no time to examine those specimen closer. Such results thus need to be presented at another occasion.

Information about nomenclature used in the 2003 publication and about the citation of this species description

Nomenclature for dorsal/ventral setation of juveniles and adults used in this old species description of mite H. palustre was my own invention and is no longer used by me for practical/systematic reasons of comparison.

The nomenclature I introduced at the time of that species description for the pattern of individual fields that cover the thickening of the cuticle (proterosoma shield) on the anterior dorsal side of the proterosoma is still retained by me to this day. I still consider this characteristic in adults to be systematically relevant.

Cuticular shield of H. palustre stabilizes muscle origins at the dorsal proterosoma, close to the mouthparts, © Stefan F. Wirth

The original species description is cited as a 2001 publication on the Acarologia abstract page and is cited as 2002 publication in the PDF of the article provided by Acarologia as open access publication. In fact it was accepted for publication in 2001 and finally published in 2003. Thus I sometimes cited it as 2003 publication, but 2002 would be a correcter citation too. At least the full species name must be Histiostoma palustre Wirth, 2002.

Link to the original species description:

© Stefan F. Wirth 2023, Berlin

Short story: The human nature – A Fairy Tale?

A father lived deep in the woods in a small house with his two growing children, a daughter and a son. The mother did not love the woods and had therefore left her husband and children many years ago.

The father taught his children to be one with nature. And so the son knew all the birds that lived in the forest, not only the many species, but also each individual, which he could always recognize by the sound of its personal melody. The daughter loved the trees and she too knew all kinds and every single tree.

The father had once moved his family from the big city to the woods because he believed that it was the big cities that robbed people of their minds and natural instincts, thus inciting destruction and violence.

In seclusion, he wanted to allow himself and his family to become part of nature again, because he hoped that it would be his descendants who could survive the fate of the world. It quickly became too much for the woman. She missed the narrow streets, the crowded markets, the idleness and the noise of the busy city. And so she fled one dark night and never came back.

The man taught the children how to make fire with stones, and which berries, fruits, and mushrooms are edible. And for a while the father lived with the son and daughter in happy and calm harmony. Only the wind occasionally swept through the green treetops and became the accompanying music in the symphony of birdsongs and the whispering, greening and howling of the wild animals.

But the older the children got, the more they bothered about the seclusion in which they lived. Increasingly, they no longer saw the wild nature around them as an asset, but as a constant threat.

The birds shit on their heads, ate the berry bushes and fruit trees bare. At night the ominous cry of the owls robbed them of their sleep. And the trees, bushes and weeds grew closer and closer to the family’s small wooden house with the crooked chimney.

And it seemed to the children as if the forest wanted to slowly and cruelly suffocate them and their house. And so, estranged from the father, both son and daughter conspired, met secretly in the forest clearing near the river and discussed that the father was probably not in his right mind to just let nature happen. And they realized that only those who know how to subjugate nature would survive.

And when the father went out to get food and firewood, the children began to tame, to control, to clean up wild nature. The son showed the daughter how to make a bow out of wood fibers and thin branches. The daughter explained to the brother which flints could be used most efficiently to quickly start a fire.

And every day, punctually when father left the house, they would meet in the forest clearing and together they would plan to shoot as many birds as possible with the bow. And it was not long before the magnificent symphony of the birds over the great, wide forest fell silent forever.

And brother and sister worked hard to carry the many small dead bodies to the forest clearing by the river, where in the late afternoon, before their father returned, they kindled a huge campfire in which they burned the dead birds of the forest in droves. And they couldn’t resist the smell of the simmering, tender meat, so they ate a feast that prevented them developing any appetite later when their father was preparing supper.

But he wasn’t surprised because he firmly believed that modesty always comes when people have found their way back to their original nature.

When there were no more birds in the whole forest, brother and sister hunted mice and rabbits and everything that was small and rustled or squeaked and frightened the siblings. Here, too, they ate and became fuller and fuller every day. But the father, exhausted from his long excursions and almost blind to everything that contradicted his ideals, continued to ignore the changes in his children and the forest.

And now it was only the increased hunger that moved the siblings to kill all the deer and pigs. And at the feast in the clearing by the river, they filled their bellies almost to the point of bursting. But the father, who was getting older and more tired, still didn’t notice any of this. And now the weasels, foxes, and wolves died of their own accord, so that the brother and sister laid aside their bows, because they only had to collect the dead animals.

There were so many that the siblings slept into the afternoon for many weeks and then indulged in gluttony while the father progressively lost his sight and noticed nothing.

Like pigs, brother and sister had become so fat that they had great difficulty making their way through dense undergrowth and over gnarled tree roots to the clearing by the river. And so they decided to clean up the forest and once and for all to remove all vegetation between the house and the forest clearing.

To this end, both set fire to different places. But they completely underestimated the destructive power of the flames. At first only individual trees burned, but then the flames combined and became a raging and violent conflagration, which first completely burned down the house with unspeakable heat and breakneck speed and then took hold of the entire forest. Brother and sister had no choice but to throw themselves into the river and stay there, mostly completely submerged, for two days until the fire died out, until the forest was completely burned down.

And when they emerged from the river, there was only a soot-blackened wasteland with gnarled skeletons crouching on the ground, the sad remnants of what was once the forest. A huge cloud of soot and water vapor covered the sky and the sun, everything was gray and dark and the smell of death and ash filled the air.

And the father? He was on his way back, with bundles of firewood hauling in a cart and bags full of fruit slung over his shoulder, when he saw the blaze racing toward him. He parked the cart and put his bags down. And in that moment he finally realized what had happened. He would never see his children growing adult, other people would never follow the example of his family and found a new dynasty of purer, nature-loving people with his children.

And just before the firestorm reached his body, shattering his head and evaporating his brain, just before his body thereafter completely crumbled to ashes, tears welled up in his eyes and he exclaimed in a hoarse voice, „So this isn’t a brain spectre, it’s indeed human nature, destruction and killing!“

Oh, if only brother and sister had known the way back to the city. But that was far away, and the path was completely burned and turned into a wasteland. The siblings had little strength left to anticipate and mourn the death of their father.

They laboriously built a small, shabby hut out of the burnt ruins of the house, in which they lived together in a very small space from then on. It wasn’t long before the brother knew every moss and lichen, while the sister knew every stone and every dry waterhole in this forest desert. And so they ate mosses and lichens, which they crushed to pulp with all kinds of suitable stones. And they drank the water from the shrunken river, which was more like thick, foul-smelling slime.

Both, brother and sister, grew thin as spindles, and days turned into months and months into years. Since we are in the year 2085 and cold winters have long since ceased to exist even far from the equator, the former forest slowly turned into a real desert of sand and stone. The rare rain filled the riverbed just enough for brother and sister to drink. Mosses had become rare. And so the siblings were eating lichens and the putrid bank mud of the river, when a dispute arose among the siblings over the privilege of eating.

So they divided the one shabby hut into two shabby huts, which they built along the river bank at a suitable distance from each other, so as to remain close to their feeding grounds but as far away from each other as possible. But occasional quarrels were not absent. Ultimately, the initial quarrel turned into deep anger, and then abysmal hatred. The brother, now a man, began throwing heavy stones at the sister whenever she tried to approach the succulent heap of putrid riverweed and filthy mud he had first spotted.

But the sun shone relentlessly and hot winds sanded the desert landscape more and more. The bed of the river shrank, and the huts of the quarreling scrawny siblings inevitably drew nearer and nearer to one another. In the end, the brother saw no other way out than to burn down the sister’s hut, whereupon she grabbed an old, rusty and long nail and drove it right into the brother’s skull.

She buried her dead brother where the forest clearing had once been, and yes, she shed a tear in the process. And more tears followed, day after day and month after month. After another year, the sister died, not of hunger, nor of thirst or a force of nature, but of loneliness. How can you go on living when there isn’t even someone to hate, she thought just before closing her eyes forever. Her body crumbled to dust that the wind carried up into the air. And the dust became one with the ashes of the forest and those of the father, and finally fell down on the brother’s grave. In the end there was nothing left but the desert.

© all copyrights (text, idea, drawings) by Stefan F Wirth, Berlin, 3 January 2023

Teaching: Ich als Naturalist – Me as a naturalist

Bumble bee Bombus sp. in Berlin, copyrights Stefan F. Wirth 2021/2022
Honey bee Apis mellifera in Berlin, copyrights Stefan F. Wirth 2021/2022
Deutonymphs of the microscopically tiny mite Schwiebea cf. eurynymphae (Acaridae, Astigmata) formally attached to beetle Phosphuga atrata under the bark of felled tree trunk of Tilia platyphyllos in urban park Rehberge in Berlin, copyrights Stefan F. Wirth, 2021/2022
Larvae of beetle Oryctes nasicornis from Italy with associated gamasid mites under studio light conditions, copyrights Stefan F. Wirth, Berlin 2016/2022
Land crab Metasesarma obesum under studio conditions, copyrights Stefan F. Wirth, Berlin 2017/2022


Ich biete Unterricht, Förderkurse, Vorträge und Fortbildungskurse zu den Themen Naturkunde, Naturschutz, Artenvielfalt, Ökologie, Klimaschutz und Evolution an sowie Unterricht oder Vorträge zur Naturfotografie oder der Naturfilmerei. All dies entweder auf Honarbasis oder via Anstellung. Bitte entnehmen Sie weitere Informationen meinem Menüpunkt zum Thema Unterricht und Lehre. Selbstverständlich verfüge ich über Qualifikationsnachweise zu meinen diversen bisherigen Lehrtätigkeiten sowie meine fachliche Kompetenz. Bitte beachten Sie hierzu auch meinen Menüpunkt Curriculum Vitae.

Doch was sind eigentlich meine Themengebiete? Im Folgenden finden Sie interessante Fragestellungen aus meinen Kompetenzbereichen.

Was ist ein Ökosystem? Welche Ökosysteme sind gut untersucht, welche eher nicht? Wie gut kennt man die Artenvielfalt von Mikro-Lebensstätten in Deutschland, und was ist über deren biologische (ökologische) Zusammenhänge bekannt? Was ist denn eigentlich eine Art, was sind denn dann Zwillingsarten, und was versteht man gar unter einem Artenkomplex (kryptische Artengruppe)? Ist das Aussterben von Arten ein normaler Bestandteil der Evolution oder ist das Aussterben einer Art immer zwingend ein alamierender Hinweis auf eine (evtl. menschengemachte) Naturkatastrophe? Wieviele Arten aus allen Organismengruppen weltweit kennen wir, und wieviele in etwa kennen wir noch nicht? Warum kennen wir viele Arten, sogar in Deutschland, noch immer nicht? Wie erkennt man neue Arten, und wie ist eine sogenannte Artbeschreibung aufgebaut? Ist der Mensch eine Tierart, und wo im Stammbaum der Tiere ist er dann anzusiedeln?

Warum sind ein Wald, ein Teich oder eine Wiese Orte für interessante Entdeckungen, und zwar insbesondere auch für Kinder? Was lebt denn da, und wie ist es an seinen Lebensraum angepasst? Was haben unterschiedliche Arten in solchen Lebensräumen eigentlich miteinander zu tun? Und wie beobachtet man Tierverhalten am besten? Wie dokumentiert man es aussagekräftig, um sein Wissen später mit Freunden oder über soziale Netzwerke teilen zu können?

Wie kommt es zum sogenannten Global Warming, der globalen Klimaerwärmung? Wie können wir sie nachweisen? Warum ist sie zu einem beträchtlichen Teil menschengemacht? Und welche Auswirkungen haben Klimaerwärmung und die Ausbeutung natürlicher Ressourcen (Energiespeicher, Rohstoffe, wie zum Beispiel Tropenholz) für die Zukunft der Menschheit und die Artenvielfalt auf unserer Erde. Welche Auswege erhofft man sich? Woran wird derzeit gearbeitet?

Was benötigt man zur Naturfotografie, was, wenn man zusätzlich oder alternativ auch noch auf gutem Niveau filmen möchte? Was ist grundsätzlich wichtiger: Das Equipment oder das Bild, das zuvor im Kopf des Fotografen oder Filmers entsteht? Muss taugliches Equipment immer ultra-teuer sein? Welche Software eignet sich am besten zum Editieren? Was genügt dabei den Ansprüchen von Anfängern, was benötigen Fortgeschrittene und Profis? Wie filme oder fotografiere ich draußen in der Natur? Wie hole ich stattdessen die Natur in mein Fotostudio und inszeniere sie dort so, dass es aussieht, als habe man im Freien gearbeitet?

Dies sind alles mögliche Themen, die in meinem Unterricht, meinen Kursen oder Vorträgen vertieft werden können. Beliebige weitere Fragestellungen aus den Bereichen Naturkunde, Biologie, Ökologie und Evolution arbeite ich gerne für Sie aus.

I offer lessons, remedial courses, lectures and advanced training courses on the subjects of natural history, nature conservation, biodiversity, ecology, climate protection and evolution, as well as lessons or lectures on nature photography or nature filming. All this either on a fee basis or via employment. Please see my menu item on the subject of teaching for further information. Of course, I have proofs of qualifications for my various previous teaching activities as well as my professional competence. Please also note my menu item Curriculum Vitae. 

But what are my topics? In the following you will find interesting questions from my areas of competence:

What is an ecosystem? Which ecosystems have been well studied and which not? How well do you know the biodiversity of micro habitats in Germany and what is known about their biological (ecological) relationships? What is actually a species, what are sibling species, and what is meant by a species complex (cryptic species group)? Is the extinction of species a normal part of evolution or is the extinction of a species always an alarming indicator of a (possibly human-made) natural disaster? How many species from all groups of organisms worldwide do we know, and roughly how many do we not yet know? Why do we still not know many species, even in Germany? How do we recognize new species and how is a so-called species description structured? Are humans an animal species, and if so, where do they belong in the animal tree?

Why are a forest, a pond or a meadow places for interesting discoveries, especially for children? What lives there and how is it adapted to its habitat? What do different species actually have to do with each other in such habitats? And what is the best way to observe animal behavior? How can you document it meaningfully so that you can later share your knowledge with friends or via social networks? 

How does the global warming come about? How can we prove its existence? Why is it largely human-made? And what are the effects of global warming and the exploitation of natural resources (energy stores, raw materials such as tropical wood) on the future of humanity and biodiversity on our planet? What exits to avoid emergency situations are we hoping for? What are scientists currently working on to ensure a healthy human future? 

What do we need for nature photography, what if we also want to film at a good level in addition or as an alternative? What is fundamentally more important: the equipment or the image that is created in the head of the photographer or filmmaker? Does suitable equipment always have to be ultra-expensive? Which software is best for editing? What meets the requirements of beginners, what do advanced and professionals need? How do we film or take photos outdoors in nature? Instead, how do we bring nature into our photo studio and stage it there in such a way that it looks as if we were working outdoors? 

These are all possible topics that can be deepened in my teaching, courses or lectures. I would be happy to work out any other questions from the fields of natural history, biology, ecology and evolution for you. 

all copyrights Stefan F. Wirth Berlin 2022

Mate guarding of a juvenile female in mites of the Histiostomatidae (Astigmata, Acariformes)

Male of Histiostoma sp. guards a female tritonymph, copyrights Stefan F. Wirth 2005-2022


A strategy to avoid male competition for females


Some mites of the Histiostomatidae practice so-called mate guarding of subadult females in order to have an advantage in the intraspecific competition between males for adult females. My SEM image shows a male on top of a female, which is still inside its tritonymphal cuticle. Inside the tritonymphal cuticle, the adult female is already developed and shortly before hatching. Before hatching, the legs of the new instar are folded under the body side. The new second leg on the right side is visible in the SEM, because the weak cuticle of the old leg broke off. This strategy to avoid sexual competition is quite common with Histiostomatidae. Due to insufficient mite material and not longer available clear ecological data, I determine the long haired adults of my old SEM series with caution as Histiostoma sp., it seemingly was found around sap flux on a tree trunk in Berlin. The species is not identical with Seliea pulchrum (= Histiostoma pulchrum), typically known from sap flux. The distance between the male legs 1 and 2 in the photo is about 0.1 mm. These SEM objects were seemingly chemically dried for the scanning electron microscopic procedure. The photos were taken around 2005 with an older SEM at FU Berlin. © Stefan F. Wirth Berlin 2022

Mites, Biodiversity, evolution, species extinction, new species

More Specialists are needed to study our biodiversity: recognizing and describing new species, redescribing known ones, mapping their distribution and understanding their ecological role in an ecosystem.Thus we have to support our children and students to become fascinated by nature.

Also interested laypeople, hobby researchers and nature lovers can contribute to species preservation and nature conservation (and thus climate protection) and encourage their children or relatives to study biology or a similar subject.

Es werden mehr Spezialisten benötigt, um unsere Biodiversität zu studieren: neue Arten zu erkennen und zu beschreiben, schon bekannte Arten neu zu beschreiben, ihre Verbreitung zu kartieren und ihre ökologische Rolle in einem Ökosystem zu verstehen. Daher müssen wir unsere Kinder und Schüler dabei unterstützen, sich für die Natur zu begeistern.

Auch interessierte Laien, Hobbyforscher und Naturfreunde können einen Beitrag zum Arten- und Naturschutz (und damit zum Klimaschutz) leisten und ihre Kinder oder Angehörigen für ein Studium der Biologie oder eines ähnlichen Faches animieren.

© Stefan F. Wirth, Berlin 2022

I provide advices and information about the topics mites (in general, in your house or your company and in a hygiennic context), biodiversity, correlation biodiversity research and climate change, speciation processes, describing new species, species extinction, taxonomy for private people, educational institutions, e.g. schools or university students. Please see my menue item „Angebot biologische Beratung…“

Ich biete Beratung und Informationen zu den Themen Milben (allgemein, in Ihrem Haus oder Ihrem Unternehmen oder im hygienischen Kontext), Biodiversität, Korrelation Biodiversitätsforschung und Klimawandel, Artbildungsprozesse, Beschreibung neuer Arten, Artensterben, Taxonomie, für Privatpersonen, Bildungseinrichtungen, z.B. Schulen, oder Studenten. Bitte beachten Sie meinen Menüpunkt "Angebot biologische Beratung..."

Biodiversity research in the US, is the so called American Way always a good basis?

A collegue from the field of entomology recently wrote me his impressions about the situation of scientific fundings in the western world, as he travels around and stays with each of his feet in another country. He said that everybody knows about the importance of the biodiversity on earth and that consequently everybody agrees that research on the biodiversity deserves to be funded. But he continued that this does not mean that the same people would agree that biodiversity research requires experts and that experts would even need to be paid. Thus many of his former students in the US or Germany need to survive with temporary jobs other than their expertises would require.

But also an international unbalance of financial resources, available for fundamental research in entomology or for example acarology (my discipline) can lead to experts being sorted out, although they would be urgently needed. The focus, based on the considered eligibility of research, changed withing the last 25 years. As before Germany was a hotspot for high-quality research in the fields of evolutionary biology, systematics and biodiversity research, that focus of interest is now located in the USA. They invest more money into these sciences than all European countries together.

This can additionally have consequences for the quality of such kinds of research. It is no secret that the general educational level in the US is at least in some areas comparably low, many people don’t speak foreign languages, they often don’t travel abroad, and they live in midst of a mentality, which says „America first“. Biodiversity research would in the old German world of science regularly be connected with many „but consider that…“ conditions. The American way, in some cases, might want to have it easier. They might say: what’s the problem? What do they want to have? Yes, right, they want the numbers of all discovered species. They ask for numbers, thus we do our best to give them numbers, as fast as possible.

Some privileged US-researchers might even misuse their financial power to decide, who in other countries is and who is not. But I say in a rhetoric „you“: Use your fundings to involve as many suffering experts from abroad as possible, instead of center too much work and responsibility on yourself, you won’t have enough time due to too many species, which still need to be discovered and described.  Don’t work too fast and don’t risk to become too superficial. Each species deserves time. Share the work with others and make science benefit from the different kinds of backgrounds in different areas of the world.



A mite of the Histiostomatidae, found in Amsterdam in its original substrate as example for the topic „Acarology“


All copyrights (also of SEM photo): Dr. rer. nat. Stefan F. Wirth, Berlin July 2020

Mite Histiostoma piceae

The mite Histiostoma piceae Scheucher, 1957 is a member of the mite family Histiostomatidae (Astigmata, Acariformes). Scheucher discovered the mite based on all instars from spruce, infected by the bark beetle Ips typographus. She collected her samples in Regensburg, Höbing (bei Roth) and Harz. Scheucher reared her specimens on potatoes and bran, but describes that her cultures did grow well only to some degree.

According to her findings,  phoretic carrier (hosts) is the bark beetle species Ips typographus, she also found deutonymphs rarely on some staphylinids. She discovered that free living non-deutonymphal stages develop on fresh detritus, while deutonymphs appear only on old detritus („after it was for a longer time removed from the trees“, „wenn der Mulm einige Zeit aus den Bäumen entfernt ist“). I could like Scheucher culture the mites on potato, but a bit better in their original gallery substrate. Under laboratory conditions, they indeed did not rear very well in both kinds of cultures.

I collected H. piceae between 2000 and 2004 once from a wooden log infested by I. typographus in Berlin, then got access to microscopic slides from Europe in the collection of John C. Moser (Louisiana, USA) in 2007 and 2009, then I collected samples from Ips typographus and I. cembrae in Central Croatia (publication Wirth, Weis and Pernek, 2016) and found out that H. piceae is not restricted to I. typographus, but also to its sibling species I. cembrae. I finally collected the mite from I. typographus galleries between 2015 and 2016 in Western-Siberia near the city Tyumen.

I repeatedly observed deutonymphs of H. piceae under natural conditions (bark samples directly after the excursions) to develop in very high numbers, then attaching to all available arthropods nearby, smaller bark beetle species and numerous bigger mites of different groups, such as for example oribatids.

Published recordings of H. piceae from other bark beetles than I. typographus and I. cembrae are doubtful and need to be named Histiostoma cf. piceae. In some cases with I. typographus additionally present, I interpret the mites to have switched from their regular carrier (host) to an adjacent gallery of e.g. another smaller bark beetle species. In other cases, the existence of similar looking species new to science needs to be tested. In cases of determinations by non specialists from bark beetles other than the above mentioned two beetle species, it needs to be assumed that these people could not differ between similar mite species, such as Histiostoma trichophorum Oudemans, 1912, Histiostoma ulmi Scheucher, 1957 or Histiostoma crypturgi Scheucher, 1957.


I never before published the full set of SEM and light microscopic photos from these  times (except of my article about host specificity). In this explicite photo publication here on my homepage, I herewith publish SEM-photographs, objects sputtered with gold, which might be not unique to science, but very rare.

Any subsequent research on this mite in Europe is not happening (a few not too relevant findings are published by a former Russian colleague). Reason is that modern science does not understand, especially not in Germany, that fundamental research in applied fields is worth to be funded. It is for example known that deutonymphs of different mite species on bark beetles regularly carry fungus spores (different fungus species, just sticking on the mite’s cuticle), discovered by John C. Moser and confirmed by several of my own publications. This phenomenon is still not closer studied. Fungus transport into bark beetle galleries can influence the micro climate there.



Male and female of Histiostoma piceae, A venter of male, B dorsum of male, C mouthparts with Digitus fixus, D dorsum of female, E side-frontal view to female; Berlin 2002-2020, copyrights Stefan F. Wirth



Deutonymph of Histiostoma piceae in ventral view, collected in Western Siberia, 2015 – 2016, copyrights Stefan F. Wirth


Systematics: Histiostoma piceae is according to my phd thesis from 2004 and according to my more recent research findings a member of a clade (monophylum) within Histiostomatidae with most species associated with bark beetles (Scolytinae) or other bark inhabiting coleopterans; these phylogenetic findings are based on morphological characters.

Mite Histiostoma maritimum

The mite Histiostoma maritimum Oudemans 1914 is a member of the mite family Histiostomatidae (Astigmata, Acariformes). Oudemans discovered the mite based on its deutonymph only from a Dutch island. The German acarologist R. Scheucher found the species in 1957 in mud at the riverside of Regnitz and for the first time could rear H. maritimum and was able to redescribe it by its adult stages, especially females look morphologically conspicuous due to a sclerotized cuticula shield around its copulation opening. She reared her specimens on potatoes, mud and bran, but describes that her cultures did not grow well.

Phoretic carrieres (hosts) are beetles of genus Heterocerus, some carabids and according her findings also rarely some staphylinids.

I discovered H. maritimum between 2000 and 2004 repeatedly in sapropel around ponds in an old gravel pit area in Berlin, forest Grunewald, named „im Jagen 86“. They were mainly attached to the beetles Heterocerus fenestratus and Heterocerus fusculus, but could regularly also be found on the carabids Elaphrus cupreus and Bembidion sp.. I could several times rear the mites, like Scheucher almost unsuccessfully on potatoes, but well on cadavers of their carriers. I thus reconstructed a so called necromenic life-strategy for H. maritium. This means that a phoretic stage ascends a carrier, but never leaves, instead it awaits the carrier’s natural dead to develop on its cadaver (published in my phd thesis, online, 2004).

I will not publish my full set of SEM photos from earlier times here. Some photos will be saved for one of my upcoming paper submissions in scientific and peer-reviewed journals. In this photo publication here on my homepage, I at least publish some interesting SEM-photographs, based on objects sputtered with gold and a subsequent critical-point-drying procedure.

Adults of Histiostoma maritimum: A left male, right female, B, C, copulation opening, D dorsal view to female with mouthparts and copulation opening

Systematics: H. maritimum shares morphological characters of deutonymph (setation, apodemes) and adults (mouthpart details, shape of Digitus fixus) with species like Histiostoma feroniarum, H. insulare, H. litorale, H. palustre, H. polypori, H. myrmicarum. This might indicate a separate clade, but according to the old findings in my phd thesis, also a paraphyletic grouping including these species is thinkable.

Copyrights Stefan F. Wirth, 10 June 2020

Male-Gender discrimination in the natural sciences – unacceptable?

When I was a little child, we used to play all kinds of common child’s plays, such as touch and go or even football, under the motto: boys against girls. But only a few years later in the primary school, such a motto did not exist any more at all. Our teachers wore weird beards, flared trousers or turtleneck pullovers, knitted by themselves, and were pipe smokers, women almost looked the same. They were children of the 1968s, a kind of late hippies in a catholic primary school. Regarding discipline, they were not too tolerant, but there was no separation between genders. We learned that in friendships, the personality of somebody counts, not the gender. I did not differ between male or female school friends. As a young child, you expect this modern and tolerant spirit even growing with the time, but it did seemingly not, times today instead sometimes show a harsh backwards orientation unfortunately.



wächter fertig

„The sad one“, ink on paper, Berlin 2016, copyrights Stefan F. Wirth



Everybody talks about gender. They say the female gender is on purpose suppressed by power-hungry men. When I search in social networks for tags, such as #Berlin, #forest, #city or #flowers, I see mostly half naked women, promoting themselves in a tight bikini or by literally simply presenting their breasts. Simple minded neutral observers, may be aliens, would think: ah, interesting, different strategies! While men fight with diligence for their succeeding in life, females choose the more simple way by just showing off.

But I am not simple minded, and I do not know any simple minded people, that’s why I of course analyze such observations and conclude: no, no, no, these are all misconceptions, when it seems that women might use their sexual attraction on men, when they need attention or want to continue their career, then the reality is that they just prove self-determination and independence. When we read in the news that again an almost forgotten Hollywood-star showed off for the Playboy, then we exactly know that she wants to emphasize her feminist ethos by presenting herself like that for the male readers of the journal, simply to set a signal against sexual subjugation to men. Easy to understand! And when unsuccessful actresses accuse famous film directors of sexual harassment from 40 years ago, then this does not indicate a cheap effort to catch public attention at the expense of somebody else. No, no, no, they were just cruelly intimidated in these times decades ago, felt menaced and helpless in a world dominated by powerful and unscrupulous dominant males. It needed so much time to come out in public about what happened, as the today spirit of time finally allows public condemnation without any official trial. So, we learn that feminism did not reach its final peak in the 1970s and 80s, no its going on, and needs to go on and even must be more powerful than ever before, as males still instinctively feel a pressure to suppress women. I support and accept this fight for equality of genders. Viva ultra feminism!

BUT: I would like to draw a line, which should not be crossed. The world of sciences, especially natural sciences, needs to be rid of all kinds of absurd gender discrimination in both directions. My generation of males was obliged to complete either a military service or a civil service. My civil service took me 15 months of my life time. All in all, I lost two years until I could begin studying at a university. Females of my generation finished their studies about two years earlier, which offered them already enough advantage in proceeding with their academic careers and in finding positions. While males in the natural sciences need to prove their work-power permanently by publishing one paper after another, even when unemployed, females go in maternal leave, after they gave birth to their children, and years later of course get in the easiest way a position, without having learned to publish and perform research even without any salaries at all. This goes on costs of the quality of science itself, it thus is fully unacceptable.

But let’s continue: A male with thirty peer-review publications and a woman without any peer-review publications at all apply for the same scientific position. What happens today is in such a situation that based on the so called gender-equality rules, based on woman’s officers and women’s quota, the female applicant needs to be preferred regardless of her qualification and diligence. I had rejected applications, where they officially argued with a necessary preference for a female candidate, based on gender-equality rules. In other cases, they argued to have already decided for another candidate, which was in such cases always a woman. I know a former colleague, who I visited for a short research stay and who had introduced me to his girl friend, who was the same time his official diploma student. A desaster! I heard about a male biologist, who officially criticized the male-gender discrimination in the scientific world in Germany. He was bullied throughout Germany and even Europe so much that he needed to leave the continent, performing now his research in Mexico or Australia, I do not remember. A scandal!

Male gender discrimination in the word of sciences harms the future of science at all!


Berlin, 10 June 2020, copyrights Stefan F. Wirth

Systematics and biology of termites and about their phoretic associations

They live in eusocial communities, but are not closer related to ants or bees. Termites belong to the cockroaches.


Queen, king and castes


Usually one queen and one king are reproductive and act as heads of the nest. The different work fields of a nest are executed by infertile specimens, which can show very different and specialized body shapes. The diversity of different castes is in phylogenetically „primitive“ taxa lower than in „higher developed“ termite groups.


As example specimens of a deadwood species from Italy


This species was found in deadwood of a small forest in Portici (Gulf of Naples, Italy) and might represent the taxon Kalotermitidae. This taxon branches off rather basically  in the systematic tree of termites. Nest work can be taken over by nymphs of later alates.


deadwood-termites from Italy, Youtube: copyrights Stefan F. Wirth, April 2020



How is wood-eating possible?


Wood eating termites bear bacteria and protozoans  in their digestive tracts, which perform the digestion of cellulose.


Evolution, sister taxon and endosymbionts


Termites (Isoptera) evolved within the cockroaches (Blattodea). According to modern systematics (e.g.  Beccaloni & Eccleton, 2011) the cockroach taxon Cryptocercidae is the sister-clade of the termites. But there are controversial theories existing.

According to such reconstructions, the last common ancestor of cockroach taxon Cryptocercidae and termites possessed bacterial and protozoan endosymbionts. Molecular data proved that endosymbionts in both groups are closely related to each other. The last common ancestor of both groups showed in case of their indeed sister-group-relation a tendency towards social communities. Cryptocercidae live temporarily in bigger groups together with their offspring.


Subsocial lifestyle in Cryptocercidae


Cockroaches of the Cryptocercidae as putative sister taxon of termites live inside galleries in deadwood and feed on wood fibres. At least one parent and its nymphs live subsocially inside their galleries. Cryptocercidae adults and nymphs groom each other, and parents feed juveniles with wood fragments afer these had passed their anus openings.


According to recent systematic/ phylogenetic reconstructions the Kalotermitidae belong to the basically branching termite groups. Such basic groups of termites still show a low diversity of castes only.


Associates, commensalism and phoresy


Like ants or bees, termites share their nests regularly with associates of other groups of animals,

often mites and nematodes. Some of these organisms use termites as carriers for a transport over bigger distances. details of such associations between insects and mites are not well studied yet. But carrier-passenger-situations with transfer („taxi“-) purposes are called phoresy. Phoresy ist mostly considered as a neutral association between different organisms and is thus interpreted as commensalism. Commensalism is differed from strategies like parasiticm or symbiosis and requires that two organisms in association do not harm or noticeably benefit each other. The term commensalism often includes associations, in which the true context for both organism partners is simply not understood yet.


Not yet mites of the Gamasina (Parasitiformes) were reared in greater numbers out of my Italian termite substrate. They might represent phoretic cohabitants of those termites. Other mite species of different mite groups (Parasitiformes and Acariformes) were only found in smaller numbers and died out too quickly for collections and determinations under my culture conditions, unfortunately already before the beginning of my shootings. seemingly microclimatic conditions had become too unfavorable.


Copyrights Stefan F. Wirth, Berlin 2019 – 2020, all rights reserved