(A) Artificial song patterns used in this assay. (B and C) Chain index of D. melanogaster (B) and D. simulans (C) flies to artificial songs that carry various IPIs. Time-courses to the IPIs shorter (top) and longer (bottom) than 55 ms are shown. Time windows for three temporal phases are hatched in gray. (D and E) D. melanogaster (D) and D. simulans (E) responses in three temporal phases to artificial pulse songs of varying IPIs. Original time traces are shown in Figure 3B and 3C. Responses to artificial sine song, and pulses of 15, 35, 55, 75, 95, and 105-ms IPIs are color coded in blue, red, green, sky blue, pink, orange, and brown, respectively, in panels (B–E).