The Monopsis genus consists of 16 species, all of which are indigenous to South Africa where they can be found from Namaqualand to the southern Cape, east to KwaZulu-Natal and north to Limpopo.

Monopsis variifolia, synonymously known as Lobelia variifolia or Parastranthus variifolius and commonly known as Butter Oneye, is a South African endemic perennial found growing in the Western Cape province from Porterville to Wolseley growing on damp clay sites. From spring to late summer, it produces lovely eye-catching yellow flowers.