I spotted something moving very slowly along a wall in the house this morning and took a close look. I thought maybe it was a bagworm at first, but a couple of experts on Twitter, Colin Foote @MothIDUK and Richard Lewington confirmed it as the larva of the Case-bearing Clothes Moth, Tinea pellionella. These are sometimes colloquially known as bagworms, but they’re not fully fledged bagworms, that word is reserved for a group of moths known as the Psychids.
Now, I’ve almost certainly seen the adults of this species, although there are several very similar Tinea adults that are almost indistinguishable, so I couldn’t tell you for certain. But, I’d definitely not seen the insect in the larval stage…as with the bagworms (the Psychids), the Case-bearing Clothes Moth makes a home for itself from fragments of materials it finds when it hatches from its egg – wool and fur – for instance, which it can also eat, although it does dine on feathers in bird’s nests too. The unrelated Psychids might also use bark, wood, sand, and lichen. The case-bearer wraps itself up in its case for protection and camouflage. It’s perhaps the ultimate in mini-beast home-building. There may well be some larval silk spinning involved in building these cases and bags.
It’s a not dissimilar strategy to that used by the leafroller moths (the Totricids, from the same root as torque), which roll themselves up in a leaf of their larval foodplant. But, it’s a stark contrast to the silken larval nests made by the likes of the Brown-tail, and the Oak Processionary Moth, and very, very different from the strategy adopted by others that make themselves look threatening using lurid colour schemes, thorns, hairs, and spines, or false eyes to ward off predators, and make them seem unpalatable.
One more thing…best not to encourage this species to live in your home, its larvae do have a penchant for fabrics.