Abstract
To date, no mayflies have been described from Cape Verde, an archipelago of volcanic islands in the Atlantic Ocean. Based on the material collected on two islands, Santo Antão and Santiago, two species of the genus Cloeon Leach, 1815 (Ephemeroptera: Baetidae) are described based on larvae and imagines. Cloeon morna sp. n., collected in Santo Antão, and C. sidadi sp. n., collected in Santiago, have 3-segmented maxillary palps and tapered labial palps of larvae. The new species can be distinguished from each other and from other West-African species of the genus mainly according to details of the lateral spines on larval abdominal segments and characteristic colourations of vitta and terga in female imagines and colours of male turbinate eyes. Affinities to the West African species of the genus are discussed.