Behrensia conchiformis

The caterpillar is difficult to detect, as it rests stretched out along the length of a twig of Snowberry, Symphoricarpos albus, its larval foodplant, and it closely matches the Snowberry twig in colour and in thickness. Its grip is rather firm, and the caterpillar is unlikely to be dislodged by beating. It is to be found (if it can be found at all) in June. For pupation it must be supplied with some bark. It constructs a fairly tough cocoon on the surface of the bark, incorporating into the cocoon fragments of bark and lichen. If you cannot see the cocoon in the accompanying photograph, that was the intention of the caterpillar that built it. The pupa overwinters.

The adult emerges in March or April, and, at a casual glance, it looks like the usual brown and grey nondescript noctuid. But when a freshly-emerged Behrensia conchiformis is examined with a lens in strong sunlight, parts of the wings are seen to shine spectacularly with a brilliant highly reflective structural green iridescence. One supposes that this beauty has evolved because it offers the moth some selective advantage, but just what that advantage is, only it knows.