A neat thing about Eri silkmoths is that they led to the production of Ahimsa silk that didn't require the death of the pupa. Throw this idea into a fantasy setting, and you could have some producers boiling the cocoons and killing the pupa and others waiting for it to hatch. The latter method might produce less thread per cocoon, but it keeps the druids, moth spirits, and potential "Silk Wyrms" (as Umbran suggested) happier.
Or, perhaps an evil druidic? cult has uplifted and modified silk moths such that they begin capturing and peeling humans. (Eww!)
Another option is to back things up a step. Perhaps the tailor doesn't know how this amazing foreign cloth is produced and is on a quest to find out. This might have elements of travel epic (Sinbad!), exploring a new culture, and industrial espionage. In this case, a thief of some flavor might make sense.
Yeah Ive been reading some Chinese legends about the discovery of Silk making by Lei-tzu (aka Xi Lingshi) when she was out collecting mulberries for her sick parents, which she later shared when she married the Yellow Emperor giving China the monopoly until the later smuggling of Silk worm eggs and Sericulture to Khotan and thus India. (and later two Monks smuggled eggs to Rome)
so I’m thinking that Silk is an exclusive material of Moth Spirits who live in the Fae realm of Ta-Lo (thanks MCU).
and because its got moth fairies and tailors I want a fairytale feel to the adventure “once upon a time there was a brave tailor who decided to set out nd find his fortune”
1. our tailor discovers a mulberry wood crate washed ashore, inside lies a young women, naked but wrapped in silk cloth.
She is injured and needs help - and a new dress (I want to have some custom-made tailoring/sewing challenges scattered in too

)
2. She wants to be taken back to her grandmother who lives in a sacred grove which is protected by Silk wyrms
3. Various challenges ensue, the girl is being chased by ???
* a creature that peels the skins of humans might work here, insect themed?
4. The sacred grove is of course in the Fae realm, they get in but to get out the PC must face the grandmothers test - a choice of seven silk worms of different colours, 4 are poisonous (wyrms), 2 are normal and one is the key to Ta Lo.
5. The Tailor gains a silk worm egg and knowledge of sericulture. Maybe a friendly moth companion and some valuable enchanted silk.
so -
A) why is the girl in the box? ( maybe Evil stepmothers fit a fairytale motif?)
B) who is chasing them?
C) what challenges should the PCs face that allows them to use Sewing/Weaving skills
D) other advice?
NB I didnt realise that Silk Wyrm was an actual DarkSun creature until now. im going to modify them so they are more insectile - giant centipede-like