I am Alejandro, I work at Bangor University, North Wales analysing shells. Last week we have received a batch of freshwater mussels from USA and we have found something quite interesting. On the top of one of the shells (Lampsilis sp.) there was a rocky aggregate made of pebbles and sand grains attached to the shell. When I removed it and looked under the microscope I saw what it seems to be a mouth opening and an anus opening. The "teeth" in the structure seems to be bioformed though I do not think they belong to the actual animal rather than being some kind of solidified mucus. Inside of the case we can see a coppery coloured head and what it seems a pair of jaws and some appendices when we looked through the anus oppening. I think it may be a larvae of Glossomatidae though I am not an expert on insects. I would be quite interested in knowing what it is and I thought it could be also interesting to show the case shape because I have not found a picture describing its structure in internet.
Hi Alejandro - yes it’s certainly a caddisfly case and sounds like the occupant is still in there. I cannot identify further but it does appear that in this case (no pun intended) the larva appears to have been rather ambitious in its selection of stones - perhaps its bravado.