This monotypic genus is a common weedy annual of Europe that is naturalized in northeastern states, but it does not seem to be spreading within Ky. or more southeastern states (W). The few records here date only from 1893 (Pr) to 1947 (or perhaps an unverified record in 1975). Aethusa (also known as "fool's parsley") is somewhat toxic to mammals when fresh, involving a polyene "aethusin" (Hotti & Rischer 2017). It can be confused with the mor edible Anthriscus sylvestris ("cow parsley") but differs as follows (Clapham et al. 1981): fruits ca. 3-4 mm long (versus 4-5 mm), ovoid, acute without beak (versus lanceolate with 1-3 mm beak); partial involucres with 2-3 long linear downwardly deflexed bracts (versus 4-6, not deflexed); plants mostly 30-70 cm tall (versus 60-100 cm), summer-annual or rarely biennial (versus biennial or short-lived perennial), largely glabrous (versus densely puberulent on stems and leaves), with nauseus smell when crushed (versus pleasantly aromatic like licorce or aniseed).