Cheng here is Jiang's friend and is a Marbled Silk Moth, a solitary species four times the size and twice the intelligence of their Spotted Silk Moth cousins. They have most of the anatomical features of predatory moths, including articulated forewings and a fused beak-like set of inner mandibles, but actually have mostly similar habits to their cousins, their size being the main reason they are not social. They are not farmed because their solitary nature works against it and they are not nearly stupid enough to fail to realise where their nests are going, but sometimes a Marbled Moth egg (which is practically identical) will get mixed in with a clutch of Spotted Moth eggs being shipped from one farm to another. Usually they're kept away from the farm's moths because they get will get upset when their daughter flies away at the age of about one year; Spotted Moths routinely forget what their own eggs are (aside from that they are important in some way) and become agitated when they hatch because they are not sure if this is supposed to happen. Obviously, recognising any egg as something other than an Important Round Thing is rather beyond them.

Cheng stayed because, when she was thinking of leaving, Jiang was deathly ill. She instead sat on Jiang's tail to keep her company. These days she sleeps in a pile of silk cloth under Jiang's bed.

Her parents know there is something strange about their daughter, but they have absolutely no idea what it is.