grub found in our leather tanning pit

grub found in our leather tanning pit

Observation - grub found in our leather tanning pit. Description: it moves like a catterpillar, has a retractable, slimy tail, and a pair of very small antenae. there were loads of them in the tanning solution for the last month (different stages), and they are eating the leather. what are they?

it moves like a catterpillar, has a retractable, slimy tail, and a pair of very small antenae.
there were loads of them in the tanning solution for the last month (different stages), and they are eating the leather. what are they?