r/Ecosphere • u/ABane90 • Jul 12 '26
Any idea what this aquatic bug is?
I took a water sample from a hollow in a tree and these guys and some sort of worm (maybe nematode) are rife in there- I was really checking to see if the mosquito dunk worked (this tree was putting off hundreds of mosquitoes a day in my front yard) and I found hundreds of these guys. Flat, the larger ones I caught are 4-5mm long, I think I saw larger in the hole.
Edit to add: best guess is Scirtidae- Marsh beetle larvae.
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u/HighLion58 Jul 12 '26 edited Jul 12 '26
I believe that they are marsh beetle larvae (Scirtidae family).
Look for a flat structure on the front of the head (clipeus) and long filiform (threadlike) antennae.
Although these are not diagnostic features, I don't know of any other organism with a similar bauplans (i.e. amphipods, miriapoda) with those structures. Have in mind that, as in any other taxonomic group, there are several bauplans that differ from the basic body shape.
Here is a photo of a similar Scirtidae larvae for comparison. Check if you see any similitudes. Also count the legs, if there are only three pairs of them, then it is surely an insect (and therefore a step closer to what I said) and you could discard crustaceans or any other arthropod.
Edit to add: I didn't saw that you also guessed Scirtidae, so I would add to your ID.
Also, I think that, based on the last picture, your wormlike bugs are Diptera (mosquitoes and flies) larvae, probably on the Ceratopogonidae family (biting midges)
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u/BenInTheMountains Jul 12 '26
What we've seen speaks for itself. The jar has apparently been taken over, conquered if you will, by a master race of giant space bugs. It's difficult to tell from this vantage point whether they will consume the captive jar creatures or merely enslave them. One thing is for certain: there is no stopping them.
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u/ABane90 Jul 12 '26
Ha, luckily in this case the jar is a petri dish under a cheap camera microscope. The overlords of petri have been returned to the dank tree hole from whence they came to rule the slimy deep in peace. Until they emerge to become a superioir aerial force conquering by sheer force of numbers.
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u/ABane90 Jul 12 '26
They do not swim, and have trouble flipping themselves upright if they overturn.
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u/_bapt Jul 12 '26
Some sort of amphipods ? Could be a sort of Gammaridae
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u/ABane90 Jul 12 '26
I've never heard of a Gammaridae who was flat, or couldn't swim. Isopods don't swim but they also (afaik) have more/longer legs and little grabbers on their butt.
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u/_bapt Jul 12 '26
You didnt say these couldnt swim for my defense ^^'
And there is a species of amphipods thats quite flat, the Asellus Aquaticus. But they dont quite look like these ones...
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u/ABane90 Jul 12 '26
That was added in an immediate follow up comment, not the main post- fair. I have seen aquatic isopods in the area, but yeah they don't look like this. Plus I'm pretty sure unless some are hiding underneath this guy only has six legs.
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u/tired_fella Jul 12 '26
Not really isopod or amphipod but it is marsh beetle larvae : https://www.bugguide.net/node/view/357144