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Two different forms of cryptic species-complexes in mites of the Histiostomatidae (Astigmata) from bank mud and bark beetle-galleries and their significance for applied biodiversity research

Biologe ISSN 2750-4158

Stefan F. Wirth, acarologist, freelancer, Berlin, Germany

Citation: WIRTH S. F. (2021): Two different forms of cryptic species-complexes in mites of the Histiostomatidae (Astigmata) from bank mud and bark beetle-galleries and their significance for applied biodiversity research. Biologe (ed. Stefan F. Wirth), category : original scientific papers volume 1 (2021; 2022) , 1-7. URL:


In biodiversity research, knowledge of species numbers is the basis for planning environmental protection and climate research. However, the taxonomic work is made more difficult by cryptic species complexes in the world of organisms. Careless determinations of similar species must be prevented. For a beter understanding, examples from different animal groups are given. Using two species complexes of the mite taxon Histiostomatidae (Astigmata), two different forms of cryptic species complexes are presented in detail. Based on three species from a group associated with bark beetles, an example of a species complex is presented in detail, in which all stages of development look confusingly similar to one another. On the other hand, four species of mites from the bank mud of standing waters can only be confused with one another on the basis of their phoretic dispersal stage (deutonymph), while the adults differ distinctly. The meaning of such species complexes is discussed in the evolutionary and applied context. It is critically pointed out that too few specialists are funded worldwide and few taxonomists have to work too quickly, so that there is a risk of cryptic groups of species not being taken into account in surveys.

Keywords: cryptic species groups, evolution, biodiversity research, Acariformes, Histiostomatidae, Astigmata, phoresy, Histiostoma piceae, Histiostoma Scheucherae, Histiostoma piceae, Histiostoma ulmi, Histiostoma palustre, Histiostoma litorale, male morphology, SEM, Histiostoma maritimum, Scolytinae, Carabidae, sapropel


Biodiversity research is an essential fundament for disciplines like climate research and climate changes and thus contributes to an understanding about, how we humans need to treat our own environments. A main aspect of biodiversity research besides species monitoring is the evaluation of how many species we have. Specialists need to recognize and scientifically describe new species, especially, when it for example comes out that a complex of very similiar species contains more species than expected before (e.g. Laska et al. 2018). In tendency researchers in the field of biodiversity focus most on vertebrates in temperate regions and generally less in invertebrates (Titley et al. (2017).

The number of recently existing species in numerous cases is still unknown, especially in taxa of small organisms, such as mites. Due to a lack of specialists and due to a lack of fundamental research fundings, relatively much is known about direct pests of human sources, such as Varroa or Tetranychidae mites. But within the major clade Acariformes, ecological contexts and numbers and distribution of species of some free living taxa of Prostigmata and Oribatida/Astigmata are still an open field, even in Central Europe, e. g. Germany (Wirth, 2004).

This is despite the fact that for example phoretic mites, which use other arthropods as carriers for dispersal, can have highly complex relationships with their phoretic hosts, thus being of interest from the evolutionary, the ecological and even an applied point of view. The latter is discussed for example in context with different bark beetles, which their mites might affect by acting as vectors for fungus spores (Klimov & Khaustov, 2018).

Cryptic species complexes are a topic that is currently being widely dealt with in science. Such species complexes are characterized by the fact that they are difficult or impossible to distinguish morphologically. However, they can be clearly differentiated from one another using barcoding (e.g. Kameda et al, 2007), behavioral or ecological studies. Crossing experiments are a frequently used ecological method. Because according to the biological species concept, individuals of different species either cannot be crossed with one another or the offspring of such a hybridization is not fertile (e.g. Sudhaus & Kiontke, 2007).

Crossing experiments are particularly suitable for the investigation of cryptic species complexes in species that have a rapid life cycle and, due to their small size, can be accommodated well in standardized conditions. Such organisms are, for example, free-living nematodes of the Rhabditidae (e. g. Sudhaus & Kiontke, 2007) or mites of the Histiostomatidae (e.g. Wirth, 2004).

The cryptospecies phenomenon, which means that closer investigations show that animals once attributed to the same species actually represent several species, can in principle occur in the entire animal kingdom and in plants and fungi too (Shneyer & Kotseruba, 2015). Previously known subspecies are often given their own species status as a result. One example are the two monitor lizard species Varanus niloticus and V. ornatus (e. g. Böhme & Ziegler, 2004).

In this monitor lizard research mainly ecological differences to V. niloticus have been studied. As one of the results, V. ornatus does not have a diapause in summer, which is a distinct difference to V. niloticus (Böhme & Ziegler, 2004).
As an unusual phenomenon, a case of parthenogenesis was even observed in V. ornatus, but not in V. niloticus (Hennessy, 2010) so far. However, morphological differences between these two monitor lizards were known even before, for example relating to aspects of the dorsal drawing. But the authors named above were able to provide evidence that these morphological differences do not occur gradually, as orgininally assumed, but rather distinctly.

Another example of two sibling species (the most simple form of cryptic groups) that have been identified as different species by molecular biological studies are Homo sapiens and H. neanderthalensis (e.g. Prüfer et al., 2014). Originally it was assumed that H. neanderthalensis was a subspecies of H. sapiens. This is for example supported by the proven cultural exchange between the two species and the great morphological similarity. In the meantime, however, morphological findings such as the morphology of the nasal duct of the Neanderthal man have also supported the genetic findings (Márquez et al., 2014). However, very recent studies show that Neanderthal genetics have entered the lines of H. sapiens (Hajdinjak er al., 2021). As a result, both forms have crossed and produced fertile offspring. It remains to be seen whether this will possibly dismiss the concept of two species again.

Since the aim of all studies of cryptic species complexes is to find distinctive differences in the areas of morphology, ecology or barcoding (or all approaches together) that distinguish one species from all others, ultimately clearly definable, very closely related species remain in case of successful studies.

If the cryptic organisms are members of an organism-socialization, such as parasites and their hosts, the idea that a proven host specificity can be an indicator for a certain species of a cryptic complex is obvious. In fact, Wirth et al. (2016) for example postulated a host specificity for the phoretic mite Histiostoma piceae and its hosts, the bark beetles Ips typographus and I. cembrae. Nevertheless, relationships between associated species are usually not studied extensively enough to be able to unequivocally identify certain species on the basis of for example their hosts (Wirth, 2004).

Since cryptic species represent nevertheless separate species despite their extraordinary similarity, they are subject to the species concepts. As a result, they form different niches and can therefore appear sympatric in the same living space (e. g. McBride et al., 2009). This makes it difficult for biodiversity researchers and systematics to investigate the real numbers of species in such habitats.

If, instead, cryptic species are not sympatric, but distributed in adjacent areas, this can for example indicate that an allopatric species formation has either not been completed for a long time or is even still in the process of speciation (e. g. Gollmann, 1984).

Animal species that have different developmental stages can appear cryptic, i.e.  being morphologically confusingly similar, with regard to all these developmental stages, such as for example certain phoretic free-living nematodes, which then additionally have to be studied ecologically or genetically (e. g. Derycke et al. 2008).

Other species can hardly be distinguished morphologically with regard to a certain developmental stage, which is particularly common, but differ distinctly in other developmental stages, which are more difficult to find. Very similar looking lepidopteran caterpillars of sibling species (e. g. Scheffers et al. 2012) can be more commonly available than their adults, which might be easier to distinguish.

As a specialist for mites of the family Histiostomatidae (Astigmata, Acariformes) I will in my further argumentation refer to my biodiversity studies on these mites and explain the difficult situation for describers of new species based on several specific histiostomatid species, some being phoretically associated with bark beetles and others associated with different coleopterans from muddy sapropel-habitats around ponds in Berlin/Germany.
In connection with these cryptic groups of species, reference should be made to the applied difficulties in connection with biodiversity research. I am referring to the fact that, for a variety of reasons, often only a certain juvenile stage (deutonymph) is used for species descriptions (e. g. Klimov & Khaustov, 2018 B), although cryptic species can occur sympatricly in the same habitat and in many cases not be sufficiently differentiated from one another on the basis of just this one stage.

In Histiostomatidae as in most Astigmata taxa, the deutonymph (in older publications hypopus) represents the phoront, being adapted morphologically and behaviorally in getting dispersed by insects or other arthropods. This instar has no functional mouth, possesses a ventral suckerplate to attach to its carriers and a thicker sclerotization against dehydration. The deutonymph is often collected together with its phoretic host. Bark beetle traps are for example a common source, where dead deutonymphs still on their hosts come from and are subsequently forwarded to acarologists, who then are of course unable to create a mite culture in order to have also adult instars available for species descriptions  (e. g. Klimov & Khaustov, 2018 B) and other taxonomic purposes. This paper shall clarify, why it is instead necessary for a clear species determination to have the deutonymph and additionally at least adults available.

In this publication two cryptic species complexes from the taxon Histiostomatidae (Astigmata) are presented as result of my original scientific work. On the one hand morphologically very similar representatives of the Histiostoma piceae-group, which are originally associated with bark beetles (Scolytinae), on the other hand similar looking representatives, which are bound to insects in the area of ​​the banks of ponds with digested sludge (sapropel). It needs to be emphasized in that context that those herewith introduced two cryptic clades are phylogenetically not closer related to each other.

The presented bark beetle mites (chapter 1 in results) can only be distinguished morphologically by very gradual characteristics, in terms of phoretic deutonymphs as well as in terms of adults. However, there is a tendency towards host specificity (e.g. Scheucher, 1957), which is why there could be a permanent spatial separation of the species despite common occurrence in the same region.

The mites from the sapropel in the area of ​​the pond banks (chapter 2 in results) are presented on the basis of a certain area in Berlin (Germany), where they appeared sympatric. Unlike the bark beetle mites, they are morphologically clearly distinguishable with regard to the adults, but have morphologically very similar deutonymphs, which essentially only differ from one another in degrees.

Based on the representatives of two different cryptic species groups presented in this work, it should be shown that a sufficient range of morphological features for systematic and taxonomic differentiation and characterization of species can only be available if at least two developmental stages of a population can be studied. It is also pointed out that high-resolution optical methods can uncover a possibly systematically relevant variety of morphological features that would otherwise remain hidden. It is suggested that a suspected host specificity cannot always be used to differentiate between very similar species and that cryptic species can be found sympatricly on the same host as well as in the same habitat. The main aim is to show that there is a risk of confusion and a risk of underestimating the existing biodiversity if only the deutonymph is used for taxonomic purposes, just because it is for example easily available, when the host is captured. Nevertheless species descriptions based only on the deutonymphs are unfortunately still surprisingly common.

Due to the lack of sufficient research fundings and a corresponding decrease of experienced specialists, trends to remarkably simplify determinations and species descriptions are about to manifest themselves. Non specialists or less experienced acarologists increasingly try to recognize or describe new species based on the availability of deutonymphs only, because these phoronts are often easily accessible as bycatch of entomological material. It is mistakenly assumed that faster procedures could accelerate the level of scientific knowledge about the biodiversity of astigmatid mites (Wirth, 2004).

Material and Methods

Chapter 1 is an illustration of the current state of my research about a cryptic bark beetle-associated group of species. Problems and questions are additionally shown both on the basis of existing, in part own, literature. Chapter 2 is about four species of Histiostomatidae that were recorded from an old gavelpit area in the urban Berlin forest Grunewald, named „Im Jagen 86“, located 52° 29′ N, 13° 14′ E. This chapter focuses specifically on Histiostoma maritimum, collected between 2002 and 2012 (and also between 1999 and 2000 during my diploma thesis). Besides H. maritimum three other species were found in the same area and habitat: Histiostoma palustre, collected once via deutonymphs from a beetle of Genus Cercyon in 2002 and reared in culture over about two years on moist decomposing potato pieces, Histiostoma litorale, isolated as adults from sapropel mud once in 2002 and Histiostoma n. sp., reared only one generation long from adults to adults in 2019, inside sapropel-mud samples with moss growth and moist decomposing potato pieces.

Mites of H. maritimum were collected as deutonymphs on the beetles Heterocerus fenestratus (rarer on Heterocerus fusculus) and Elaphrus cupreus from sapropel around two ponds in the named area. After different experiments, mites developed successfully on beetle cadavers on 1.5 % water agar in Petri dishes (diameter 5 cm) at room temperature (ca 20°C, summer 2002). Three cultures (one cadaver of C. elaphrus and twice each time two cadavers of H. fenestratus) were observed over a period of about three weeks (additionally small pieces of beef heart were added to all these cultures to maintain suitable food sources). Adult mites were stored in 80 % ethanol for about 5 days and then critical point dried for SEM studies. Photos were taken by an analogous medium size camera via a Philips SEM 515 and later developed. Still unpublished copies from 2002 were scanned in a high 600 dpi solution and as tiffs via a CanoScan Lide 2010 in 2021. Restauration and picture quality improvement were performed via Adobe Lightroom. The areal panorama of the former multiple pond area was captured in September 2018 via a Dji Mavic Pro drone at a height between 30 and 50 m and subsequently modified into black and white.

Setal nomenclature follows Griffiths et al. (1990).


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RAW Berlin as a cultural center in Germany’s capital


An inspiring composition of terrace, window, gate, trashcan and graffiti, copyrights for photo Stefan F. Wirth, June 2021

The RAW (Reichsbahnausbesserungswerk) extends between Warschauer Strasse, Revaler Strasse and Modersonstrasse in the Berlin district of Friedrichshain. The former railway area, which was closed in 1995, is considered to be the largest contiguous and culturally used fallow area in Germany.

Graffiti art giving the old architecture an own kind of dynamics, copyrights for photo Stefan F. Wirth, June 2021

Today the ruins are used culturally in a variety of ways. In addition to several clubs and art galleries, there are sports facilities, art studios and various take-out stands.

Self-government and graffiti art

The area is under grassroots self-government.

Atmosphere during a summer day, copyrights of photo Stefan F. Wirth, June 2021

You can already see art without having to enter galleries, namely in the form of graffiti art, which blends harmoniously and inspiringly into the partly crumbling terrain.

Skate hall and mosaic of architecture, daily life remnants and graffiti

Sports activities are also revealed to the visitor very quickly when entering the area. For example, the skate hall, which opened in 2004/2005, is the only indoor skating facility in Berlin and is internationally well known in that sports scene.

But during my short visit on a summer day afternoon in end of June 2021, I was most impressed by the mosaic of architecture elements, Graffiti and signs of daily life.

A corner close to the entrance from Revaler Straße, copyrights of photo Stefan F. Wirth, June 2021.

All copyrights Stefan F. Wirth, 27 June 2021

Reawakening at very early spring

Morning mist

Forest in the morning, tree stems covered by a foggy most, borderless steam wraps slowly rising in the air and disappearing there tracelessly.

Forests as moisture reservoir, being released in the morning due to the awakening warmth. Morning mist is nothing else than a fog, only some meters over the ground. Consisting like each fog of numerous water bodies in gas conditions, which condensate due to the cold night and seem to have springled all plants and even insects and other sleeping animals with tiny water drops.

Especially in arid environments, that morning mist watering is most wanted and essential for surviving.

With the rising sun, warmth moves the misty clouds up, where they cover the forests in a mysterious light, before the fog disappears.


Consisting of all rainbow colors, each color of the spectrum being defined by a specific wave length. But sunlight also consists of physical components, particles, called solar wind.
Light as essential source for life on earth, sunlight as energizer, basis for the production of oxygen. Warmer sun beams as reawakener of a sleeping forest.


They bloom most early in the year, do not avoid to attract early insects inmidst of snow layers: snowdrops, winter aconites and crocuses.

Snowdrops (genus Galanthus) generate thermal energy due to the absorption of sunlight. This energy is essential for growth processes in cold environments.

Winter aconites (Eranthis hyemalis) have their blossoms only opened in the sunlight. Blossoms are closed over night. Opening and closing are temperature dependent growth processes. The blossoms themselves are resistant against cold. When temperatures rise to 10 – 12 degrees, first honey bee visits can be observed.

In crocuses (genus Crocus) blooming depends on the availability of moisture and warmth. Some species bloom in autumn, others in the late winter period.

All early blooming plants save nutrients as energy resources in tubers or bulbs.

Blue hour

When the sun disappears behind the horizon, an explosion of colors in red or yellowish cover the sky. In fact indicating the end of a day, in some cultures even officially a new day was dawning, when the sun disappeared, such as in Judaism, Islam or ancient Germanic peoples.

Saying „the sun is setting“ is a relict of a geocentric model of perspective. Not the sun is moving, but the observer.

When the sun is far enough underneath the horizon, the blue light spectrum dominates and creates a shiny blue sky, forming a photogenic contrast to the silhouettes of trees and landscape structures.


The only recent Trabant of our earth, presumably sirvivor of two or even several natural earth satellites in early times of our solar system.

Reflecting sunlight at night, lightening up the sky in the dark. Orientation aid for nocturnal animals, especially insects. Rhythm generator for the reproduction periods of numerous organisms.

The only extraterrestrial body that was so far ever visited by human beings. The first, which might be colonized before Mars.

All copyrights Stefan F. Wirth, Berlin March 2021

The details about snow


In former times, when people lived in a mystic world, where elves, dwarfs, leprechauns and talking wolves did their dreadful state of affairs in the midst of dark and impenetrable huge forests, people thought that even the old trees in the woods had their own thoughts.

Park Rehberge in Berlin

Uncontrollable, sounds, the snorting of the deer, a mysterious hidden, permanently changing shades in a cold and misty twilight.


A forest is only then a forest, when a high concentration of trees is given. Woods bear a great number of species, produce a majority of oxygen in our world; they are huge reservoirs of water and stabilize the ground with their tangles of roots.


Snow consists of ice crystals. Their formation within clouds depends on the presence of ice nucleating particles and temperatures lower – 12°C.

Crystals possess a hexagonal symmetry, being prism-shaped at lower temperatures and dendrite-shaped at higher temperatures.

Temperate deciduous forests hibernate without functional leaves. Most trees throw off all leaves already in autumn to be protected from desiccation in winter frost periods.

Layers of snow are excellent thermal conductors and additionally protect all life underneath from frost damages in the cold season.

Waiting for the spring time

Most life forms hibernate together with their leafless trees. Especially accumulations of deadwood contain remarkable numbers of species, such as insects, spiders, mites or nematodes. Some already begin under their snow cover to prepare themselves for the warmer season.

When all snow is gone, winter colors in red, yellow, brown and some green reappear. Early blossoming plants are already germinating.

Cancel Culture as a threat to modern constitutional states – Cancel Culture als Bedrohung für den modernen Rechtsstaat

Cancel Culture is a modern phenomenon mainly coming from the United States and negatively influencing increasingly European countries, such as Germany. A main tool of cancel culture is for me the so called "Me-Too" movement, according to which an accusation against a person does not need a proven evidence any more and preferably immediately harms the accused person existentially. 

A recent case is the medial debate about alleged domestic violence by singer Marilyn Manson, who was accused by actress Evan Rachel Wood of abuse of power and a multiple wise domestic violence. Wood was in a relationship with the singer until 2010. Her detailed public accusation is from 1 February 2021 and was published on her Instagram account. Accusations by other women followed, one of them being model Ashley Lindsay Morgan. 

No proofs and no trials were presented, but Manson was already harmed still the same day of Wood's publication: His record company Loma Vista Recordings immediately announced to cancel all further cooperation with him. The next day, his artist agency CAA parted ways with Manson. He additionally will be retrospectively cut off from the already recorded episodes of "American Gods" and "Creepshow".

I do not know, whether Manson is innocent, but in just states the presumption of innocence applies until the conviction. Seemingly not any more valid in the US, a shame, a picture of a declining moral of a society, for which not even Donald Trump can be blamed any more.

That easy way of cancel culture unfortunately already a longer time ago invaded Germany. Even journalists disregard all common methods of careful journalistic research. Recently for example a journalist named Laura Backes recognized already in the headline of her article in "Es ist: häusliche Gewalt (It is: domestic violence)". 

And her article ends with "And the solidarity, which Evan Rachel Wood ... and others experience in the public, shows that it is worth taking this step". Normally the German journal "Der Spiegel" is famous for its investigative journalism. This article is a bad example for it.

Singer Marilyn Manson at 2006 Cannes Film Festival, by Georges Biard, CC BY-SA 3.0,
Deutsche Version
Cancel Culture ist ein modernes Phänomen, das aus den USA kommend zunehmend auch fortschrittliche europäische Länder wie Deutschland infiltriert. Ein wichtiges Instrument der Cancel Culture ist meiner Ansicht nach die sogenannte "Me-Too-" Bewegung, der zufolge die öffentliche Beschuldigung gegen eine Person keiner überprüften Belege mehr bedarf und der beschuldigten Person unverzüglich schwerste existenzielle Schädigungen bereitet.

Ein aktueller Fall ist die mediale Debatte um die vorgebliche häusliche Gewalt, die der Sänger Marilyn Manson mehrfach praktiziert haben soll. Er wurde durch die Schauspielerin Evan Rachel Wood öffentlich des Machtmißbrauchs in der Beziehung sowie schwerer und multipler häuslicher Gewalt bezichtigt. Wood, die mehrere Jahre mit Manson in einer Beziehung liiert war, tat der Öffentlichkeit ihre unbelegten Anschuldigungen am 1. Februar 2021 über ihren Instagram-Kanal kund. Weitere Frauen folgten ihrem Beispiel und äußerten ähnliche Vorwürfe, wie zum Beispiel das Model Ashley Lindsay Morgan. 

Es wurden weder Beweise noch Gerichtsurteile präsentiert, jedoch stellten sich schwerwiegende berufliche und existenzielle Konsequenzen für Manson bereits am selben Tage ein: Die Plattenfirma Loma Vista Recordings kündigte sofort jede Zusammenarbeit mit dem Künstler auf. Am Folgetag trennte sich auch seine Künstleragentur CAA öffentlich von ihm. Zusätzlich soll er aus den bis dahin bereits aufgezeichneten Folgen von "American Gods" und "Creepshow" im Nachhinein herausgeschnitten werden. 

Ich weiß nicht, ob Manson unschuldig ist, aber in modernen Rechtsstaaten gilt die Unschuldsvermutung so lange, bis ein Schuldspruch erfolgt ist. Und genau das scheint inzwischen in den USA keine Gültigkeit mehr zu haben, was eine Schande ist. Es entsteht so nämlich das Bild einer Gesellschaft mit zunehmend rückläufigen Moralvorstellungen, das man inzwischen auch beim besten Willen nicht mehr Donald Trump in die Schuhe schieben kann. 

Der einfache Weg, unliebsame Menschen aus dem Wege zu räumen, den man eben neudeutsch als Cancel Culture bezeichnet, ist seit einiger Zeit leider auch in Deutschland angekommen. Selbst Journalisten können heutzutage unter Verzicht auf alle gängigen Methoden der guten journalistischen Praxis zuschlagen. Heute hat zum Beispiel eine Journalistin namens Laura Backes in Form eines dort als "Analyse" bezeichneten Artikels eine Cancel-Tirade gegen Marilyn Manson und eine Lobeshymne auf die "Mee-Too-" Bewegung auf veröffentlicht. Das Ergebnis ihrer investigativen Analyse nimmt sie gleich in der Überschrift des Beitrages vorweg: "Es ist: häusliche Gewalt". 

Ihr Artikel endet mit den Worten: "Und die Solidarität, die Evan Rachel Wood, Ashley Lindsay Morgan und die anderen in der Öffentlichkeit erfahren, zeigt, dass es sich lohnt, diesen Schritt zu gehen." Normalerweise ist der Spiegel bekannt für seinen investigativen Journalismus. Leider ist dieser Beitrag alles andere als ein gutes Beispiel hierfür.

Copyrights for both written article versions in English and German: Stefan F. Wirth, Berlin 4 February 2021

Berlin: Arthropod diversity in 2020 (Corona year)

I documented my nature excursions in 2020 via photography and videography with a special focus to animal macros (outside in the field) and to drone flights. There is also an underwater scenery existing. Most footage was recorded in the area between villages Lübars and Rosenthal in Northern Berlin, close to the nature refuge „Tegeler Fliess“.

The area is characterized by fields, meadows and forest parts and lays along the former GDR wall, today being a hiking and biking trail. Due to a connected mosaic of different ecological habitats, a remarkable biodiversity can there be found, even despite of the worldwide species‘ extinction based on a mostly human made global warming.

My videographic review of the second part of the Corona-year 2020, focussed on arthropod life on meadows in Northern Berlin, all copyrights Stefan F. Wirth

Some few sequences were recorded in other parts of the green city Berlin, namely in the park of the Charlottenburg Palace (beginning sequences of the video) and in urban park Rehberge und Plötzensee (the leaf beetle Galeruca tanaceti in Plötzensee and the scarabaeid beetle – systematically related to genus Cremastocheilus- in Rehberge). Crematocheilus (Cetoniinae) is a genus of myrmecophilous beetles. My individuals were not yet determined, Their existence in Berlin might be even of scientific interest. As putative phoretic vector (to carry mites for their dispersal), they are at least of interest for me, although the studied three beetle individuals did not carry mites at all. The beetles were all found in front of an ant nest intrance (Lasius niger) along the roots of an oak tree in park Rehberge.

As my scientific/ photographic/ videographic excursions happened in exactly that year, 2020, in which the normal human life came worldwide totally out of order based on the covid-19 pandemic, I decided to add this topic to the concept of my video. The video presents nature footage from my visit in the correct seasonal order, beginning with May and June, followed by July, then September/October. In front of each of those months-blocks, I added at that time some important recent news headlines about the corona-pandemic. I named these written parts „corona calendar“. The few December sequences are only dedicated to human street life, showing Berlin in the total lockdown phase, being filmed in black and white (with red recognition).

Berlin, 2 January 2021, all copyrights Stefan F. Wirth

Ant Lasius fuliginosus: Winged alates and insect/mite nest cohabitants

Ants usually reproduce via mating flights. So also the black wood ant Lasius fuliginosus, whose nest I discovered in the Berlin urban park „Rehberge“, where it was (and is) located in the depth under a spruce tree stump. I filmed them under favorable (climatic) for mating flights.

In some cases workers needed to force them to stay out. This behavior is well visible in my film.

Do ants live alone inside their nests? No, not at all. Numerous non-ant-organisms are adapted in living with them, using all kinds of tricks to be not attacked by the ant workers. A known example is the beetle Amphiotis marginata. Where do they reproduce, where does the offspring lives and develops? Semingly according to science and researcher Prof. B. Hölldobler still partly unknown. I also cannot contribute much. But: An undetermined larva of the same family, Nitidulidae, was found to be active under fruit bodies of the fungus Trametes versicolor on the nest top, adjacent to a beetle pupa (not known, whether the same species or family). When exposed to the ant trail near the fungus, the nitidulid larva was attacked, but not caught and was seemingly sufficiently defensive without a visible activity, thus may be chemically. The behavior is visible in my footage. The pupa in contrary was caught and carried away by the ant workers.

Numerous other insects, many mite species and nematodes inhabit ant nests. But some might just occasionally get in contact with a „suddenly“ forming ant nest colony, being remnants may be from former conditions, and nevertheless persist the passing ants on their crowded trails. Two species of mites of the Astigmata seemed to belong to that kind of cohabitants.

According to the visible different galleries of bark attacking insects, it is assumed that this was the way, how these mites came to their place on the inside of the (still partly well intact being) bark of the spruce stump, may be indicating that it was not too long ago felled down. Most conspicuous were the irregular shaped galleries of the bark beetle Dryocoetes autographus (Scolytinae), partly still equipped with remnants of dead beetle individuals. As typical secondary bark infesting insect, this beetle prefers harmed or dead wood. And might have been there already before or while the ant nest grew.

Film about ant Lasius fuliginosus in a park in Berlin with nest cohabitants, 2020, all copyrights Stefan F. Wirth

The mites were found free or attached to a wood insect on: the inside of the bark, which the ants use as major trail to access their main nest in the depth, means much ant fluctuation. But there was no clear indication for a direct phoretic interaction with the ants, because species one was only found as one deutonymph attached to another insect host, species 2 in different instars, rather no further ant-transport necessary.

Species one: a deutonymph on an undetermined beetle larva, later isolated and filmed via light microscope in motion. Seemingly belonging to Acaridae. Species two: two or three free deutonymphs and two tritonymphs close to bark beetle remnants, being Histiostomatidae, seemingly Histiostoma dryocoeti Scheucher, 1957. Due to the filming activities and the few mites, no slides were prepared, determinations are based on light microscopic footage and photos of living (thus not cleared) individuals. Scheucher’s description is bad and lacks juveniles, males and the female’s dorsum, the deutonymph’s drawing is almost sketch-like. Already for that reason, I determine my mites as Histiostoma cf. dryocoeti. being determined basically based on the deutonymph. Also because I could not see all important deutonymphal details, but the shape (smurf-house-roof-shaped, dorsal view) of the proterosoma, the entire body proportions, the pattern of dorsal setae (as far as visible on the photos) and especially their shape (like typically for bark-beetle-histiostomatids more or less directed forewards, but distinctly shorter than normally) as well as the leg shapes (distal end similar to Scheucher’s drawings) and the rather small rounded suckerplate and the short palposoma (ending with or before dorsal proterosoma) fit more or less to her description. The seemingly corresponding tritonymphs were not described by her, but according to my research fit at least to bark-beetle-species (dorsal structures). But paired posterior elongations are visible and might (not necessarily) indicate similar structures in adult females too, while Scheucher doesn’t show the female dorsum at all and just writes „no special features existing“ about it. Thus the tritonymphal morphology forces me to name the species with „cf.“ even more. The tritonymphal mouthparts (palparmembrane) seemingly show lateral elongations (almost fitting to Scheucher’s description).

I filmed on one day directly on the nest, mites were recorded the same day and subsequent days (end May, beginning June)at home using a light microscope with upper light and a stereo microscope.

Berlin, December 2020, copyrights Stefan F. Wirth

Copulation details of snail Cornu aspersum (4K)

I collected two specimens of the land snail Cornu aspersum from an old olive grove in the city Sorrento (Gulf of Naples, Italy) in April 2019. The land molluscs could be found in that spring season in and under flat stones and smaller rocks. They shared this habitat with bgger diplopodes of genus Julidae and the harvestman Trogulus tingiformis.

The snails are until today successfully kept in a terrarium with sufficient moisture and regular food consisting of vegetable pieces. They share the terrarium with some specimens of diplopods from the original location in Italy.

Cornu aspersum mating, film made in Berlin, all copyrights Stefan F. Wirth

The snails go in a strict diapause several times a year for weeks or months, when temperatures in Berlin grow over 20°C . After getting active again on a colder period, they often quite immediately begin to mate. My video only focuses on details of such mating procedures, especially the spermatheca transfer. I decided to cut as less as possible and to present longer sequences of copulation activities, as they have due to slow slime exchange movements and rhythmical motions a special aesthetics. I additionally intended to show that scientific behavioral studies generally require patience and time as well as interest and fascination for aspects of life.

Cornu aspersum mates reciprocally, which means that both partners transfer a sperm package and produce ovules. The mating of my footage was successful (not visible in my video), and about 20-30 young snails hatched after about 2.5 weeks after egg deposition.

Aspects of mating and copulation in Cornu aspersum are quite well scientifically studied. For example: the variation in spermathecal morphology does not depend on the sperm competition intensity in populations (E. Koemtzopoulos & A. Staikou (Zoology 110 (2), 139-146, 2007); aspects of courtship and copulation were studied by S. A. Adamo and R. Chase (Canadian Journal of Zoology 66(6): 1446-1453, 2011). According to the latter authors the typical mating behavior has a duration of about 421.8 minutes and consists of three major parts: introductory behavior, dart shooting and copulation. My video concentrates only on part 3.

Berlin August 2019 – 10 June 2020, copyrights Stefan F. Wirth

Ant cricket and beetle Amphotis marginata in a nest of Lasius fuliginosus

The ant Lasius fuliginosus builts its nests into wooden environments, for example tree stumps. In the depth it is shaped by a carton-like substance, produced by the ants and with a „domesticated“ fungus involved. When ant workers leave the nests on trails, marked with pheromones, they might seek for food (mostly aphid secretions) in distances up to 30 meters. In the area around the nest, so called foraging trails are especially busy, as different kinds of foraging substances need to be carried in, in order to feed the fungus, in order to create new cartonage and in order to feed queen, nest mates and offspring.

Such a foraging trail is of course a very attractive place for invaders (non ant species) to either capture some food from the workers on their ways into the nest, or even to attach to these workers to get a ride inside the nest too, interesting for brood parasites for example, but also for all kinds of organisms, which prefer nest micro climatic conditions and want to be additionally secured or at least tolerated by the ants. All these organisms, such as insects, mites or nematodes, even pseudoscorpions, need to have specific adaptations in order to be not attacked by the ants.

Film about nest cohabitants of Lasius fuliginosus, Berlin 2020, copyrights Stefan F. Wirth

Three examples are presented in my video. The ant cricket Myrmecophilus acervorum is a common inhabitant of different ant species. Here I found it while „walking in row and order with the ants“. That unusual tiny cricket is assumed to be able to adopt the „smell“ of a nest, which is why ant workers accept it around them. I discovered the specimen of my footage in a later afternoon (around 18:00 in May 2020) directly on top of the tree stump, in which the nest is hidden (in the depth). There it directly followed ants within their foraging walk to the nest entrances. It was directly walking with them in a row and seemed to imitate additionally antennae movements of ants. It after a while left the row of ants (unharmed and without getting a special attention) and went into a hideaway on the side of the tree stump. Generally, there is not much known about the biology of this cricket. There is evidence that it feeds on food and even brood of the ants.

Another ant trail invader is the tiny beetle Amphiotis marginata (Nitidulidae), which performs behaviors, which make its stay inside foraging trails of ants (seemingly associated with Lasius fuliginosus only) even necessary: Hölldobler & Kwapich (2017) had studied this beetle and its behaviors in detail. According to their findings, the beetle shows a complex behavior to beg for food from passing-by antworkers. Movements of its antennae are an important part of such a contact and might in the optimal case lead to a response by the ant to antennate back to the beetle’s head, and subsequently the beetle might be fed as if it were an ant conspecific. The authors describe that a beetle is not always successful. In the best case, hectic ants on their way home might simply oversee the invader (kleptoparasite), in the worst case, they might detect it as a stranger and would then attack it. For protection, the beetle is able to closely adhere to the ground with its claws, while the side edges of its elytrae are shaped downward to the ground. This way, ants are unable to lift such a beetle up and would continue their ways after a while. Hölldobler and Kwapich also mention that they observed cases, in which ants were nevertheless able to lift detected beetles up and then cut their legs off, which means the end of the beetles adventurous life. The beetle specimen in my footage found a bad position aside to an ant path, which was such busy that it was overseen and even unable to approach single workers to beg for food. The authors above found some indications that the beetle’s larvae might develop inside ant nests.

As an acarologist, I am of course interested in mites, which are associated with ant nests. I in detail was involved in research about non-native ants: in the USA (Lousiana) I did research about the leafcutter ant Atta texana and the red imported fire ant Solenopsis invicta, all in cooperation with John C. Moser. I even described a new species of astigmatid mites from S. invicta. I also did some unpublished research on native ants and thus know that also Lasius fuliginosus possesses greater numbers of mite-associates (Parasitiformes and Acariformes). As an example given in this video, we see a rather big mite of the Mesostigmata (Parasitiformes), which I could not determine closer based on my footage. Mesostigmata generally can appear as phoretic organisms (feeding for example on nematodes or mites inside the ant nests, but being carried by ant workers there), they can also invade by themselves and might appear as brood or kleptoparasites. The mite in my footage walked directly on the ant trail without being harmed. It might be like the ant cricket able to adopt ant nest scents to be protected.

Berlin, Plötzensee/ Rehberge, May 2020, copyrights Stefan F. Wirth

Macro Life in urban Parks of Berlin

Berlin is a green city. Each district has several urban parks of different sizes. Besides Tiergarten and Tempelhofer Feld in the center and South of Berlin, the northern district Wedding has an unusually large park area, the „Rehberge“ (originally connected with Schillerpark and Goethepark), which is based on several sand dunes as relicts of the last glacial period. Before the responsible governmental institutions began in the 1920th to create a large city park with sports and nature sites, the sand hills were connected by extended swamps. Today the park, to which also the location Plötzensee is belonging, consists of a mosaic of different habitat types. A cut meadow area is made for people to rest or to practice sports of all kind. Adjacent lay forest areas with partly conifers mostly, wild growing (dry) meadows, sandy areas and wetlands (around ponds and lake Plötzensee).

my film about arthropod biodiversity in the first half of 2020, all copyrights Stefan F. Wirth

There is quite a remarkable biodiversity inhabiting this urban nature refuge. Besides aquatic organisms and birds, arthropods, gastropods, lichens, mosses and different taxa of flowering plants inhabit the „Rehberge“. I did not try for this video project to seek for very rare species. Instead I just intended to record some (more or less) common macro life examples. Main purpose was a camera move through the park focused on the unusual perspective to the tiny life forms. Species names are visible underneath in the corresponding video parts.

Copyrights Stefan F. Wirth, Berlin, Rehberge/ Plötzensee, May 2020