Lasius (Dendrolasius) fuliginosus, is an European ant species of the subfamily Formicinae. The species’ name means “sooty” or “dark”, referring seemly to the very dark, shiny color of the ant. The ants are really black (unless other dark Lasius species, which are actually brown) and shiny, making them very appealing to look at. They are also slightly larger than other Lasius species. The ants have a distinctive odor (pick one up and smell your fingers!) and nest in hollow trees, and therefore are also called the smelling carpenter ants. The nest is built using cardboard-like material made of wood particles, honeydew and a species of fungus (Cladosporium myrmecophilum). The workers can sometimes be seen moving up and down a tree in a trail, with the abdomens of the returning workers being physogastric of the collected honeydew. Their trails can be very long, sometimes up to 30 meters, providing an amazing spectacle to observe.

However, the more interesting part of their biology is the way they found their colonies. Lasius fuliginosus is a social parasite… of a social parasite. The female enters a colony of the yellow-colored Lasius umbratus, manages to take over its odor, kills its queen and takes it over. Lasius umbratus in its turn does the same to Lasius niger. The Lasius fuliginosus female cannot found a colony independently and relies entirely on the Lasius umbratus workers to raise her brood. When the yellow Lasius umbratus workers decrease and the Lasius fuliginosus workers increase in numbers, the colony slowly makes a shift from a predominantly yellow color to a predominantly black color, until the last Lasius umbratus worker dies, erasing every single trace of the conquered colony.

The dependent colony foundation is one of the main reasons what makes it so hard to keep this species. There are very few cases of successful foundations. On the one side, I find this a shame, because it prevents the ant-keeper from observing their interesting behavior and enjoying their beauty, but on the other side the challenge keeps stimulating the ant-keeper’s interest.

You’ll need a Lasius umbratus colony and a fertilized Lasius fuliginosus female to raise a colony. However, it is also possible to raise a colony without Lasius umbratus, but by using Lasius niger as a host colony instead. The latter is what I’ve done. I found a Lasius fuliginosus female in May 2012, which I then introduced to 20-30 Lasius niger workers in a test tube. She was accepted by the workers and a month later, in June, I boosted the “colony” with some brood, only to find that the female had laid some eggs. You have to be very patient, because the fertility of this species is delayed. It can take some time before the first eggs appear. In August the first larvae appeared (see picture below). Although I was very excited, I was also skeptical, because this did not yet prove that the female was fertilized. The eggs could still have been unfertilized, only to produce males.

Lasius fuliginosus
Lasius niger workers and Lasius fuliginosus larvae in a test tube

The larvae did not develop into pupae before the winter arrived and I decided to put the colony in the refrigerator in order to induce dormancy. Perhaps the rest could help the colony to develop. I ended the dormancy in February 2013. In April, the colony had produced two pupae. The queen kept producing eggs and the numbers of larvae and pupae increased substantially.

Lasius fuliginosus
Many Lasius fuliginosus pupae

On May 22nd, I took another look at the test tube and when observing all pupae I came across one through which I could see the adult moving inside. There were also other open cocoons, but I could not see any Lasius fuliginosus workers between all the Lasius niger workers. So I decided to help this one out. Her mandibles were already sticking out. I took her out the test tube and gently cut open the cocoon, releasing the adult Lasius fuliginosus worker. After putting her back in the foraging area of the colony, many Lasius niger workers started inspecting her and then dragging her. She wasn’t able to walk. Perhaps the conditions in which I’ve helped her hatch were not humid enough, which caused a problem in the hardening of her exoskeleton. Eventually she was dragged into the test tube by the Lasius niger workers. I wasn’t sure if she was under attack and would end up as food. When I took a look inside the test tube, she unfortunately seemed dead. After looking again a few hours later, I could not spot her. The Lasius niger workers probably took care of her dead body. You can see her (while still alive) in the picture below.

Lasius fuliginosus
Lasius fuliginosus adult, still gray, being pulled on by Lasius niger workers: you can clearly see the heart-shaped head characteristic of Lasius fuliginosus

I did not give up. The queen was doing fine, producing a lot of brood. There were still many eggs, larvae and pupae, but no adult Lasius fuliginosus workers. I proved that the larvae can survive without the fungus and that the eggs are viable, but something went wrong during or after the hatching of the cocoon. I was disappointed, but I still had hope.

I looked in the test tube again on June 5th 2013, and suddenly there were several Lasius fuliginosus workers between all the Lasius niger workers. They were totally healthy, accepted and functioning. There was apparently no need for me to help them hatch, because the Lasius niger workers can do the job on their own. I decided to disturb the colony as little as possible, which was kind of hard, because I wanted to watch all the time. The founding was hereby successful more than a year later from the moment I found the queen. The colony is still doing fine today, the Lasius fuliginosus workers increasing in numbers (see picture below). Now let’s hope the colony maintains as long as possible. Remarks on the care of the colony are welcome.

Lasius fuliginosus
The colony predominantly consists of Lasius fuliginosus workers now
Lasius fuliginosus
A size and color comparison between Lasius niger (on the left) and Lasius fuliginosus (on the right)

I hope this post can provide some information to other ant keepers about the biology and the founding of Lasius fuliginosus. My main advice to others would be to be patient. It took me more than a year to see the first adult worker, only to see her die tragically immediately after hatching! I also hope that other hobbyists can contribute to my knowledge and help me take care of this Lasius fuliginosus colony. I would also love to hear from other ant keepers that have successfully founded a Lasius fuliginosus colony. If you have some tips, suggestions or other remarks, please don’t hesitate to leave a comment.

More information about the colony founding in this species can be found here (Donisthorpe, 1922).

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18 thoughts on “Founding a Lasius fuliginosus colony

  1. When you introduced the female to the Lasius niger colony, did you cool them i before? And how big is the chance the Lasius fuliginosus won’y be accepted?

    (Ik weet niet of je Engels of Nederlands prefereert in de comments, maar mijn engels is niet zo goed 😉


    1. I didn’t cool them down at all. However, it is possible to cool the ants down in order to increase the chance that they accept the queen. I just monitored the ants so I could intervene when the workers would attack the queen. But I was lucky and they did fine.

      I unfortunately can’t really say how big the chance is of the ants accepting the queen, because this is actually the only time I’ve ever founded a Lasius fuliginosus colony. I tried a Lasius umbratus queen with Lasius niger before, but that queen was killed.

      But when you get your hands on Lasius umbratus or Lasius fuliginosus, it is definitely worth trying!

      Thank you for your reply (English is fine by the way)!

  2. Hi,
    Thank you for your post! This gives me hope again. I got a fuliginosus here end had an umbratus queen untill yesterday. The Lasius niger workers kind of killed her. I will try it with a newborn Lasius niger ant + the Lasius fuliginosus queen.

    I searched the web for years to find a post like yours. So thankfull!

    1. Thanks, I’m glad this post has been helpful. Too bad your L. umbratus queen was killed. Using L. umbratus as a host colony is propably better than L. niger, but it adds an extra step to the process because you have to succesfully found an umbratus colony first. This post proves that L. niger can do the job, reducing the number of steps and perhaps increasing the chance of succeeding.
      However, this L. fuliginosus queen unfortunately died a while ago with no apparent reason. I haven’t tried to found a new colony since then, but I might give it another shot soon. I hope you’ll succeed. If you do so, please let me know!

    2. Btw, ik ben van België (zoals je kan zien in mijn eerste comment) dus liever nederlands als engels 😉

      Wat geef je hen te eten? Suikerwater appreciëren ze (L. fuliginosus) hier niet. Terwijl Lasius niger en andere mieren dat wel doen.
      Na hoeveel tijd heb je trophallaxie geobserveert tussen de werkmieren L. niger en de koningin L. fuliginosus?

      1. Het is een Engelstalige blog, daarom probeer ik de voertaal Engels te houden voor de rest van de lezers. Maar ik wil wel even in het Nederlands reageren :) . Ik gaf ze honingdauwsurrogaat (zie mijn post daarover), toen ze nog leefden. In de natuur melken ze namelijk ook gewoon bladluizen. Ik kan me helaas niet meer herinneren hoe de trophallaxie verliep, ik liet ze namelijk zoveel mogelijk met rust.

  3. Spijtig dat ze gostorven is! Ik zal ook in het Engels verder doen :) I’m thinking to hold aphids for the L. fuliginosus. See how that works out. At the moment I got 2 accepted Lasius umbratus (well, Lasius parasites) I’ll try to introduce a L. Fuliginosus next year. I’m frustrated because I had a L. fuli once, that had laid eggs, but released it because it was going too slow. I don’t want to polute your post with my comments. You can contact me at [e-mail removed]

    1. Commenting is not polluting, feel free to share your thoughts. That’s what the comments section is for. :) I’ve removed your e-mail address by the way, posting your e-mail address like that will result in spam on your e-mail. Needless to say, you can safely enter your e-mail address in the field where it’s supposed to be typed, because no one can read it there.
      I wish you lots of luck next year. It’s indeed very important to be patient. Mine took very long to lay eggs and before these eggs actually hatched, so don’t release your colony.

      1. Hi again,

        I’m still waiting for the queens to have their nuptial flight, but I had a though last time: How do you deal with their strong smell? The nest must be very airy, no? Or are big tubes just fine?

        1. As far as I recall I had no trouble whatsoever with their scent. Perhaps if the colony grows significantly their scent could be an issue, but I suppose it wouldn’t be that bad with enough ventilation. I actually like their scent, so I wouldn’t even mind. Tubes would be fine, as long as the foraging area has good ventilation (preferably no lid).

  4. Hey, i just found this species of ant climbing up and down a tree yesterday in a woodland and have been reading about them for a few hours today (this post being the most helpful by far). I am tempted to try to find a queen this year and add her to my current lasius niger colony (she has 4 workers at the moment). But i was wondering.. once you had the Fuliginosus colony founded did you have to do anything about their tendency to make a cardboard-like structures or were they perfectly fine in a test tube set up? Also what did you move them into after the colony grew to big for the tube?

    1. I’ve never surpassed the test tube setup when the queen died, so I wouldn’t know for sure. I believe the queen carries around the fungus the colony needs to make the cardboard structure with (just like attine species), so maybe it’s crucial for the survival of the colony to provide with wood.

  5. I found a L. Fuliginosus queen a week ago, what i did is i introduced her to 9 fuliginosus workers, i saw a little white spec close to the queen so it is possible she has already layed an egg. I love the size of these ants, they are quite big.

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