Upper plot: Fermi 1FGL variability index divided by 10 vs. Reduc.F_sys for all detections associated with the 1FGL sources with a cross-matching with radius 30′, where colours correspond to source classes, blue for AGNs, black for HMXBs, red for PSRs, green for SNRs, light-blue for the unclassified ones, and orange for the three Special Cases Crab nebula + pulsar, 1AGLR J2021+4030 (γ Cygni region) and 1AGLR J1044-5944 (Eta Carinae). Markers correspond to AGILE variability type according to Reduc.F_sys, i.e. circles for non-variable and triangles for variable. The lower plot is obtained with association to the 2FGL catalogue with the same radius and shows the 2FGL index divided by 23. The black horizontal lines are the 1FGL and 2FGL variability thresholds, 2.32 and 1.81, while the dashed vertical lines correspond to the approximately extrapolated threshold (1.6) for the AGILE variability Reduc.F_sys parameter obtained from the correlation with the V_sys2σ parameter.