Spermacoce as circumscribed here follows the mainly Old World classification, and includes Borreria. This genus is frequently confusd in particular with Diodella, Mitracarpus, Oldenlandia, and Otiophora.
The most commonly collected species in Madagacar are S. flagelliformis, which belongs to the "Borreria" group with capsular fruits and has regularly axillary inflorescences; S. verticillata, which also belongs to the "Borreria" group and has mostly terminal, subglobose inflorescences; and S. tenuior, which belongs to Spermacoce s. str. with the fruits asymmetrical, with one dehiscent locule and one smaller indehiscent locule. The name Spermacoce stricta has sometimes been used for plants from Africa and Madagascar, but Verdcourt clarified in The Flora of Tropical East Africa (1976, p. 357) that those plants are now treated as Spermacoce pusilla. Verdcourt (1976) presents detailed descriptions and a number of illustrations for the species of Spermacoce so far documented in Madagascar.
Many species of Spermacoce are pantropical weeds, which are often overlooked and not documented. Additional species should be expected in Madagascar, in particular:
-- Spermacoce alata, which belongs to "Borreria" is known from the Comores; this species is robust and often has a yellow or blue drying color.
-- Spermacoce confusa Rendle, which belongs to Spermacoce s. str. and is found in East Africa; this differs from S. tenuior in its pubescent capsules.
-- Spermacoce remota, which belongs to "Borreria" and is known from East Africa; this species has elliptic leaves and rather well developed pubescent capsules and calyx lobes.