I found this black slug-shaped thing on a leaf by my pond in western Sweden. It's about 15 mm long, positioned on a vertical leaf (I bent it to take the picture). enter image description here

And I don't even know where to start looking. I was thinking it might be an egg cluster, but can't find anything useful without knowing at least what kind of organism made it.

  • $\begingroup$ @Canheguess I can't see any parts that I recognize as a larva (head, legs) and it's been completely still for at least 24 hours. Possibly a pupa I guess? $\endgroup$
    – picapica
    Jun 14 '16 at 17:57
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    $\begingroup$ If you see them hatching can you take a photo of that too? I've wanted to see one of these for a long time but never found one. $\endgroup$
    – arboviral
    Jun 15 '16 at 8:15
  • $\begingroup$ Nice picture and good question! $\endgroup$
    – Remi.b
    Jun 15 '16 at 11:23

After a lot of scrolling through image searches I stumbled upon the answer: this is the egg mass of some sort of horse-fly (Tabanidae). Almost identical egg mass here: http://bugguide.net/node/view/21171

enter image description here

I'm assuming I won't get a more specific answer than this.

  • $\begingroup$ Thanks for giving an answer yourself. I was really curious. :) $\endgroup$ Jun 14 '16 at 21:52
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    $\begingroup$ @AlexDeLarge Yes, me too! (Obviously enough to keep searching, compensating my lacking biology skills with patience.) $\endgroup$
    – picapica
    Jun 14 '16 at 23:09
  • $\begingroup$ I am impressed! +1 $\endgroup$ Jun 15 '16 at 0:29
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    $\begingroup$ Try to hatch them! Another nice picture is found here, which includes recently laid and mature eggs: pbase.com/image/132217026 $\endgroup$ Jun 15 '16 at 8:23
  • $\begingroup$ @fileunderwater Good idea! But I'm not sure I want to handle a bunch of horse-fly larvae, I would really prefer it if I could watch it happen out where I found it. It's just 50 m from my front door so I could go check it out quite often. Today is the third day that I've seen it in this black "mature" state, so it should happen within a couple of days (6 days seems to be a normal time until hatching) This page animaldiversity.org/accounts/Tabanus_similis says that they all hatch at once, so it's probably easy to miss! $\endgroup$
    – picapica
    Jun 15 '16 at 9:58

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