Help identify critters in my terrarium

[MarketTree]

Hello,

Can you please help me identify these critters in my terrarium and could they be harmful to Formica ants? As you can see from the pics, they're pretty small. Only about 2mm, at the most. Their head and thorax actually look a little like an ant, but their abdomen is long, flexible and will curl/contort when they move.

I baked the soil mix in the oven to kill off any invaders, so I'm assuming they came in with some moss that was added. They don't seem to be able to climb the glass walls, so I'm guessing they're not invading from the outside world.

They don't seem to have been bothering the Formica Species who are still nesting in their test tube. But I'm obviously concerned, considering I don't know what they are.

Thanks a lot!

[antnest8]

Looks like it's a Rove Beetle more specifically Paederus littoralis. At least I think, I know ant's but not beetles

I don't think they will harm your ants, some rover beetles in fact mimic ants and live with them, in a parasitic relationship, using the ant colony as protection. Still this Rover Beetle does not appear to be the ant mimicking kind

Here is a cool article about them
https://www.knowablemagazine.org/article/living-world/2020/ant-loving-beetles

[MarketTree]

Looks like it's a Rove Beetle more specifically Paederus littoralis. At least I think, I know ant's but not beetles

I don't think they will harm your ants, some rover beetles in fact mimic ants and live with them, in a parasitic relationship, using the ant colony as protection. Still this Rover Beetle does not appear to be the ant mimicking kind

Here is a cool article about them
https://www.knowablemagazine.org/article/living-world/2020/ant-loving-beetles

Very interesting! These do actually look a LOT like Paederus littoralis, as you've mentioned. However Paederus littoralis are around 1cm, whereas these are only 2mm. But I guess these could be a different, yet similar species.

So now my concern is, could these ant-mimicing beetles present a threat to my Formica colony? I only have around 10 workers at this point and I've read that they occasionally infiltrate colonies and predate on eggs & larva. However, these mystery guests don't resemble Formica in any way, I'm curious if they could still take advantage of their ability for parasitic mimicry in this case?

It's not too late to empty, sterilize and re-make my terrarium, since the ant colony is still living in their test tube. But I would obviously rather not, if I don't need to.

Here are some interesting links I've found on the subject:
https://en.wikipedia.org/wiki/Paederus
https://www.dailymail.co.uk/sciencetech/article-4301358/Rove-beetles-disguise-ants-eat-young.html

[antnest8]

Certain beetles have very specific hosts, these ones appear not to be an ant mimicking type

[MarketTree]

Certain beetles have very specific hosts, these ones appear not to be an ant mimicking type

True. At the very least, they don't seem to mimic my Formica in any way. So question, if this were your terrarium, knowing that the colony is still pretty young with only about 10 nanitics and still living in their test tube, would you place them into a fresh new setup without these unexpected guests?

[antnest8]

no, I would keep them there. As long as there is not sign of them being detrimental of the colonies heath then they are probably good for the setup.

[MarketTree]

no, I would keep them there. As long as there is not sign of them being detrimental of the colonies heath then they are probably good for the setup.

Makes perfect sense. Thanks a lot for the insights!

[MarketTree]

Ok, after doing some more research, I may have an update on these little guys...

Although, the colors & patterning do make them look a LOT like Paederus littoralis, the fact that they're much smaller leads me to believe that they're actually a larger form of springtail called Entomobrya atrocincta or possibly Entomobrya nigrocincta, which if true, would actually be great news considering they seem to be flourishing in my terrarium without noticeably disturbing my ants.

Here is a close up of Entomobrya atrocincta:


And Entomobrya nigrocincta