Next time you are near a pond, make sure you have a look for some caddisfly larvae. They are not difficult to find; many construct fantastic protective armour around their bodies, using debris and bits of vegetation. There are around 200 species of caddisfly (of the order Trichoptera) in the UK and presence of larvae is an indication of good quality, clean water.
Their life cycle begins as a clump of eggs laid in or near the water by the adult terrestrial caddisfly. After hatching, the water dwelling larva then form a case (although some species are caseless) by gluing debris together with silk – as you can see in the photo above, these larva have used bits of reed. The larva will undergo moults during this stage before adhering their case to a secure structure and pupating. The newly developed adult cuts its way out of its protective layer and emerges from the water surface, leaving behind its pupal skin. The adult caddisflies are now winged and are interestly closely related to Lepidoptera (moths and butterflies).
Sometimes different species prefer certain types of building material which can aid in identification, but is not conclusive (often microscope work is required when working with caddisfly larva.) In garden ponds the most common caddisflies are the cinnamon sedges – a group of around 30 species. To encourage caddisflies to use your pond, clean shallow water is important and sometimes overhanging vegetation is advantageous.
Being interested in both biology and art I find caddisfly larvae really brilliant as they are tiny architects in their own right! French artist Hubert Duprat even experimented with giving them gold and jewels to build their cases – you can see the result here: http://www.ecouterre.com/artists-enlist-caddisfly-larvae-t…/