Complicated lives of the little creatures!

River-flowing fast
little larvae want to catch
food that’s sweeping quickly past;
build retreats on rocks
and vegetation
with stones and pebbles glued with silk
for sheltered occupation
and at the entrance skilfully spin
a fine silk net, all set
so that they will entrap, ensnare
whatever passes,
nibbling off what’s edible,
and clean away what’s not, with care.

Proficient engineers of their home and net,
and also they’re considered yet
to have some beneficial, good effect
on river flow
and stabilising of the stoney bed below
– eco-engineers, like beavers.

When big enough and ready to pupate
– to change into that oh, so very different adult state –
they fortify, build up their homes,
the entrance seal of their retreat,
and all their innards are reformed
and soon
emerge to be …
a caddis fly!*
briefly, brief-fly,
brief adult life of flight.
 

* Hydropsychidae, the Net Spinning Caddis flies, not all the types of caddis fly larvae spin nets, some form portable tube cases!

[IP: river creatures - your poem or story must involve a river creature of some description, real or imagined]