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Monat: Januar, 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