Yponomeuta cagnagella, the spindle ermine, is a moth from the family Yponomeutidae, the ermine moths. The wingspan of the moth ranges from 19 to 26 millimetres. The head is white. Forewings are white; four longitudinal series of few black dots, first not reaching middle, second beginning near before middle, lowest including 4-7 dots; some additional black dots before termen; cilia white. Hindwings are dark grey. The larva is pale greyish-yellowish; spots black; head black.