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Tag: Stefan F. Wirth

RAW Berlin as a cultural center in Germany’s capital

The RAW

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.

Sunlight

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.

Blooming

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.

Moon

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

Misty

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.

Biology

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

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.

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

Germany on the way from a part-lockdown to a full-lockdown?

Leaders of the German national subsidiaries and the federal government, above all the chancellor Merkel, ask for stricter contact limitations. Although the current conditions in form of a part-lockdown as reaction to increasing numbers of covid-19-infections throughout Germany restrict numbers of people, who are allowed to meet up inside or outside as well as the numbers of households, to which they belong, already remarkably. All public places for socializing and cultural activities are closed, also sport clubs, public swimming trainings or outdoor sport activities in greater groups are impossible. That means, bars, cafés, restaurants are closed. Theaters and opera houses as well. Especially „smaller“ stage artists suffer existentially.

Only the german football (soccer) is still omni-present in the news reports. I don’t know why. Seemingly their games can happen under limited circumstances. I am not interested in football at all. It is also not football, which is since the beginning of the human evolution a major fundament of our societies, it’s art. Art is not only creativity, it also stands for legal criticism against all aspects of social and political interactions. Thus something important is missing. And private life? It is already in the recent part-lockdown harmed in a way, that acts against the human biology as social primates. Not only old people in retirement homes live almost under conditions of a dentation centre, also single-persons of all ages, living in smaller apartments, need to tolerate loneliness. The Homo sapiens is a social species, too much isolation can cause longtime-damages, emotionally, psychologically, in case of older people even physically. Not to forget those citizens without any kind of home. The many homeless people, especially in Berlin, are very sensible victims of recent restrictions. Are all these risks, the Germans actually are exposed to, worth to happen? I think yes, they are, if it is for a limited time and under circumstances, which do not cause more damages than the virus infections themselves. It is fact that the new corona virus can be harmful to people of all ages, especially when there are significant medical histories existing. But as all these sanctions represent limitations of our basic laws, it is important that all these limitations are reversed when the pandemic is over.

Critical questions are allowed. They are also important and necessary. And you even do not need to be a believer of modern religious movements like Qanon. I for example ask for the relevance of indirect contacts between individuals for the still too high infection numbers. When I see super markets, forcing their clients to use shopping baskets or trolleys without employees existing, who desinfect each of them before and after use, then I hear the virus clapping amused its non existing hands: „We couldn’t get you so far? Here we are, left behind from hundreds of people per day, who touched this basket or this trolley before!“ Are such contra- productive rules necessary, even when the argument is that baskets and cars force a proper distance between customers? Also in U-Bahn cars (subway etc.), trams or busses, an indirect virus transfer between passengers needs to be much better prevented . Shouldn’t it be possible to employ people, who permanently walk through the cars and desinfect seats and handrails whenever possible?

As a natural scientist and active researcher as well as reviewer for scientific journals I know that statistics generally bear many reasons for critical questions. It can easily happen that submitted natural-scientific papers in peer-review journals are rejected by the reviewers based on doubtful or insufficient or even wrong statistical methods. We read or hear in the news permanently about growing incidence numbers. Many people might think that these are given facts, about which questions or critical remarks are not appropriate or necessary. Based on the limited informations via the popular media, the following questions are very sure and from a scientific point of view of interest: How many people of a specific region, for example a district of Berlin, were tested and how many were not? In case of higher numbers of non-tested citizens, statistical means need to be used in order to extrapolate to the whole population of the corresponding region. It is important that a statistical variance within the tested people is guaranteed. There would for example be a lack of a sufficient variance, if it came out that specific genders or specific occupational groups had more reasons or even forces to participate test procedures than others. Statistical tests always have a defined probability of errors. But more and illegitime errors can for examples be added, when research institutions need to provide a defined high number of data in a defined period of time, especially when the procedure is well paid and „success“ thus economically important. According to my knowledge and experiences, scientific studies can only be finished, when they are finished. Evaluations in defined time periods with defined numbers of sample sizes are prone to error. I know from commercial institutions for market and opinion research that the time pressure is often or sometimes used for the disadvantage of a sufficient variation of test persons. Some facilitate their work by contacting such people for phone interviews, who’s telephone numbers were part of a commercial phone number trading. That means they buy existing phone numbers instead of generating them via a random number generator. Additionally/ or they facilitate statistical methods, which were developed to guarantee a variation of test persons. An example is the „Geburtstagsschlüssel (birthday key)“, which requires from the interviewer to strictly only talk to that person of a household, who was the last to have birthday or alternatively will be the next to celebrate it. If that person, so the rules, is not available, the interview cannot happen. Based on economic interests of the institutions and the time pressure, facilitated versions of the „birthday-key“ are sometimes used. Such as: asking for the birthday person in the household, and if the person is not available interviewing everybody available instead, or even leaving the birthday key completely out. Results of such „manipulated“ evaluations can be representative nevertheless. But they also might not be representative at all. There exist examples for extrapolations of upcoming electoral successes, being far removed from the real situations. What does all this have to do with evaluations about covid-19-infection numbers? I hope that independent sources regularly control the responsible research institutions regarding the proper use of statistical methods even under time pressure conditions.

In case it is made sure that indeed bars, restaurants, theaters and opera houses and not indirect contaminations elsewhere or statistical errors or manipulations cause the permanently high numbers of new infections everywhere in Germany, a total lockdown will be unavoidable. The German government and the federal state representatives will come together for further deliberations still before Christmas. This was announced in the news today. It is important that the decision for stricter measures need to take those groups of the German population under consideration, which might physically, psychologically or financially too much harmed by a full-lockdown over a longer period of time. It furthermore needs to be excluded that participating politicians have other motivations than protecting us from a pandemic virus, such as lust for power, interest in totalitarian experiments or a total lack of empathy.

Berlin, 08.12.2020, copyrights Stefan F. Wirth

Linyphiid spider visits much bigger snail and bites into mucus

During a photo shooting with a specimen of the snail Arianta arbustorum in an evening outdoors in urban park Rehberge in Berlin with artificial light from an extra lamp and camera LED light, a tiny spider of Linyphiidae (seemingly Bolyphantes sp., may be still a juvenile) appeared unexpectedly and walked seemingly targeted to the snail’s head, which was partly retracted into its shell, and stayed there for about 3 minutes, biting repeatedly into the snail’s mucus and remained subsequently each time for seconds in that position. In between it skillfully and repeatedly rearranged the positions of its legs, presumably to be not in danger to remain stuck.

While doing so, it sometimes lifted legs, when not needed, in the air, may be to reduce that way the probability to remain stuck. After about 3 minutes the spider left its position around the snail-head mucus and walked partly sidewards to the top of the shell, where it carefully cleaned its legs from remaining mucus. Due to the difficult light conditions and the unexpected spider visit, I was in this short time unable to move the camera closer to the spider (would have been technically possible, when more time and more light). Thus-close-ups with a high magnification in my video were only due to digital magnifications out of the original 4K footage. Only one biting action could be clearly documented as video file. The same short scene is in my video three times repeated to exemplify that behavior.

Spider visiting a snail, in order to incorporate mucus? Berlin May 2020, copyrights Stefan F. Wirth

The last repetition is additionally modified into slow motion. There was furthermore no video footage of legs adjusted in the air. Thus the corresponding short scene is one of numerous photos, which I captured before filming. It is unknown to me, what the purpose of the spider’s behavior was. I also did so far not find any scientific publication mentioning tiny spiders visiting much bigger snails on purpose. It looked to me as if the spider would incorporate mucus or moisture or other components excreted by the snail. I do not know, whether such a spider behavior happens regularly or at least occasionally, as I only have this one observation. I would exclude the possibility that the spider was disturbed by my photo activities in its web may be in the adjacent meadow, tried to flee and accidentally landed on the snail and just observed this unusual surrounding with its mouthparts. All looked too much like a targeted behavior with even specific behavioral adaptations. There is generally not much known about spider and snail interactions. The scientists Nyffeler and Symondson (Bern, Switzerland) published in 2001 about malacophagy in the sense of gastropod feeding by spiders (Ecological Entomology 26). But that paper deals about bigger and even big spiders feeding on snails of adequate size, which is unlike the size relations in my observed case.

It is not trivial for a spider to incorporate anything from snail mucus, as this very sticky slime acts besides other functions as defense mechanism for the gastropod. In that context the above mentioned authors cite Tretzel (1961) by mentioning that mucus production of gastropods seems to have no deterring effect on some spiders. The question then is the efficiency of spider enzymes against snail tissue, a topic, about which I did not do more literature research. According to the above mentioned authors, moisture can in malacophagous spiders be an important factor, as gastropod bodies consist to a high percentage of water. They refer to Lain (1982), who published about New Zealand mygalomorph spiders. In the case of my observation it would eventually be of interest, referring to the context above, that also gastropod mucus contains a high water percentage. More observations such as mine would be needed to find out, whether the behavior of the linyphiid spider on a much bigger slug is a specific behavior or not.

Berlin, May-November 2020, urban park Rehberge, copyrights Stefan F. Wirth