Fig. 1.

Eristalis tenax hoverflies are active during the day and inactive at night. a The black data show the locomotor activity of 43 Eristalis tenax, measured as beam breaks sampled every minute in a LAMS. In this panel, the mean data are low pass filtered purely for illustrative purposes (using a first order Butterworth low pass filter with a cutoff frequency of 0.04). The black bar under the data shows the 12:12 LD cycle. The gray data show the activity of 45 Eristalis tenax where the light was turned on for 5 h during the second night. The gray bar under the data shows the light-dark cycle. All hoverflies were 1–2 months old. Brackets show the 4 h used for statistical analyses. b The data show the mean activity during 4 h in the middle of night 2 and day 2 (extracted from the data in panel a). Significance was tested with a two-way ANOVA followed by a Tukey’s post hoc test (P < 0.0001)