Flux (F_λ) ratio (logarithmic) at 5.8 and 3.6 μ versus flux ratio at 8 and 4.5 μ. Small points: SERVS+SWIRE 18436 sources; triangles (enclosed in yellow edges): 115 sources in common with the selected sample (see Sect. 5.3.2). Cyan stars: stars; diamonds: SN. Crosses: X-ray detected sources. The colours of the triangles and of the small points from red (extended sources) to blue (pointlike sources) indicate the increasing stellarity (as in Fig. 5). The solid line is the Lacy et al. (2004) region and the dashed line the Donley et al. (2012) region.