Phenology and ecology of Philaenus spumarius and other spittlebug species were investigated during regular field surveys in 2016–2018 in four olive orchards located in coastal and inland areas of Apulia and Liguria regions of Italy, within the frame of an EFSA-funded project. Nymphal population in the herbaceous cover was estimated using quadrat samplings. Adults were collected by sweeping net on three different vegetational components: herbaceous cover, olive canopy and wild woody plants. Although the nymphs were polyphagous, they showed a strong host-preference for herbaceous plants of the Asteraceae and Fabaceae families in both the Liguria and Apulia regions of Italy: 72–88% of the total nymphs were indeed associated with these plant families. Nymphs of Aphrophora showed a similar host-preference, while those of Neophilaenus were strongly associated with Poaceae (85–100% of the nymphs were found on gramineous plants). Aphrophora alni and N. campestris showed a very low population density compared to P. spumarius. The average nymph population density of P. spumarius varied from 13 to 30 individuals/m2 in Liguria according to the olive grove and the year, and from 5 to 19 individuals/m2 in Apulia. Phenological data based on physiological time revealed that in Liguria the peak of abundance of P. spumarius nymph population was between 150 and 210 degree day (DD) while in Apulia the same peak was between 100 and 270 DD. This difference among locations could be explained by a non-linear component in the temperature-dependent development rate function of P. spumarius. The phenological pattern in the two regions is more similar if referred to chronological time. In fact, nymphs developed in Liguria between early March and end of May, and in Apulia between the end of February and mid-May. Field data are integrated with mesocosm and microcosm observations on the phenology and biology of P. spumarius.