Black biros are the pupal stage of wire coat hangars. When the imago emerges it is very soft and can pass through the smallest of holes. (It consumes the pupal shell the nutrients of which enable it to harden once it finds a suitable location in which to assume the adult imago form.)

Coat hangars remain sexually inactive while suspended but when laid flat with others they become sexually active (they are hermaphrodites) and can be hard to separate. They lay microscopically small eggs pale grey and hairy, closely resembling laundry fluff.

So far the larval stage has not been definitively observed. Some think the larvae are what we generally know as paperclips, but there is some unaccounted-for variation amongst them which doesn’t seem to be reflected in the adult coat hangar.

So far, coat hangars have proved remarkably resistant to captive breeding, and become utterly dormant under observation at all life-stages.