Starfly
Starfly is a legendary bug.
An attached note reads, “This big dark-colored shimmering butterfly is made almost entirely out of stardust.”
Ingame
Species descriptions:
- Alta: It shimmers so beautifully in the bottle! I hope it doesn’t feel lonely in there.
Sources
Can be bought from merchants:
Obtained by capturing creatures with any bugnet:
ct_starfly
Can be obtained via 
Spawnable Item Pack or 