We present new data on the ecology, natural history and geographic distribution of the recently described skipper Spialia rosae Hernández-Roldán, Dapporto, Dincă, Vicente & Vila, 2016 and compare its immature stage morphology with the sympatric species S. sertorius (Hoffmannsegg, 1804). Spialia rosae uses species of Rosa L. (Rosaceae) as larval host-plants and prefers montane habitats, while S. sertorius feeds on Sanguisorba minor Scop. (Rosaceae) and inhabits lower altitudes. Rosa corymbifera Borkh. and R. tomentosa Sm. are documented for the first time as foodplants of S. rosae. We report Microgaster australis Thomson, 1895 (Hymenoptera, Braconidae, Microgastrinae) as a larval parasitoid of S. rosae. Details of the immature stages of S. rosae and S. sertorius are shown using scanning electron microscope photographs, confirming the similar immature stage morphology, at least as regards the Iberian S. sertorius. In both species, the egg has high radial ribs, the last instar larva has branched setae covering the head, and the pupa has setae with pointed tips, barrel-like cuticular formations, and hairy mesothoracic tubercles. By extensive sampling of the species of Spialia in the region of Segovia, Central Spain, we extend the previously known geographic distribution of S. rosae to 56 new 100 km2 MGRS squares, which represents a 155 % increase. Spialia rosae is present in the northern part of the interior plateau and in the main mountain systems of the Iberian Peninsula. The main threats to the populations of S. rosae are its limited distribution range and the possible effects of climate change due to its specialization in montane habitats. The conservation status of S. rosae was previously regarded as Data Deficient (DD). With the addition of new data the species can now be evaluated as Least Concern (LC).
