LTV wavelet analysis performed on the dereddened, host-galaxy-subtracted and flux-calibrated R-band light curve of 3C 371. Top: R-band light curve. Middle: time-frequency power spectrum (left) and time-folded power spectrum (right). White contours in the left panel and the dashed line in the right panel represent variability signatures with a significance > 3σ (> 99.73% confidence level). The gray grid represents the cone of influence region affected by edge effects. Bottom: averaged variance between 1 and 100 days. The horizontal dashed line represents the 3σ (99.73%) confidence level.