Etymology. The new name "eclipsis" derives from the ancient Greek “ἔκλειψις (ékleipsis)”, meaning “eclipse of the sun or moon”. This name refers to the characteristic black maculation on the
basal half of the pronotum of the new species, which is compared to a solar or lunar eclipse.
Differential diagnosis. This new species can be easily distinguished from other members of the Rosalia (Eurybatus) formosa group by the presence of tufts of black hair at each apex of antennomeres III‒V and a black maculation on the basal half of the pronotum. Within the R. (E.) formosa subgroup, R. (E.) formosa nigroapicalis Pic, 1910 is the only species that shares the characteristic of having a pair of black spots on sides of abdominal ventrites I‒IV with this new species (Pic, 1910). However, this new species can be readily differentiated from R. (E.) f. nigroapicalis by the aforementioned characteristics as well as the narrow orange apices of the elytra (broadly black in R. (E.) formosa nigroapicalis).
