If Xylocopa, sure is X. iris due to the small size, but, if it's another genus of bee?
Yesterday. Peñaflor, Aragon, NE Spain, 300 meters, continental-mediterranean climate, dry gypsic steppe-lands dominated by Retama sphaerocaropa, Rosmarinus officinalis, Artemisia herba-alba, Salsola vermiculata, etc... with wheat fields. Size: about 15-18 mm, as a small Bombus (such as B. muscorum or B. humilis).
Can be identified?