What is "yellow-tail"

The Yellow-tail, Goldtail Moth or Swan Moth (Euproctis similis) is a moth of the family Lymantriidae. It is distributed throughout Europe to the Urals, then East across the Palearctic to Siberia. It is also found from Sri Lanka.

This species has a wingspan of 35–45 mm, the female usually noticeably larger than the male. All parts of the adults are pure white, apart from a bright yellow tip to the abdomen (larger in the female) and a small black or brown tornal mark on the forewing of the male.