Fig. 2

Morphology of a queen (a) and a worker (b) of Mystrium rogeri. Queens are larger than workers. The thorax of a queen is enlarged and made of distinct subunits, whereas the thorax of a worker is fused. Queens have three ocelli, whereas workers have none. Queens have a relatively larger gaster. LT and WG: length of tibia and width of gaster. c Digitalized outlines and semi-landmarks after sliding for queens (green circles) and worker (red circles). The differences in head morphology between both castes have been amplified by 10 %