Thumatha senex, the round-winged muslin, is a moth of the family Erebidae.

Another curved row of spots bounds the basal third of the forewing.

Larva ashy grey, very hairy, with black head.

Pupa stumpy, dark brown, in a dense hairy cocoon.

The moths fly on damp meadows, and are not rare in their flight-places; they come to the light at night.