I found many of this larvae in a pound. They stay immobile until water is moved, in vertical position with the head to the top. They are 3mm long and appear to have a head with two antennas (or tusk). Once extracted from water larvae start to move like video show. I searched in internet but i find nothing. Someone know what type of larvae is it? Thank you.

https://www.youtube.com/watch?v=Y7RXRvsNf84

sorry no-one seems to know the answer to your question.