In the Absence of fruM Function D. melanogaster Males Acquire the Ability to Court as a Consequence of Being Group-housed with Other Flies. (A) Courtship indices of males that had been isolated since eclosion prior to a 10-min single-pair courtship test. ***p < 0.001, one-way ANOVA. (B) Chaining indices of groups of 8 males that had been housed together for 4 days. ***p < 0.001, one-way ANOVA. (C) Chaining indices of groups of 8 or 5 fruLexA/fru4-40 males and courtship indices between 2 fruLexA/fru4-40 males after grouping for 3 hours, 1 day, 2 days, 3 days, and 4 days. (D) Courtship indices of fruLexA/fru4-40 males to wild-type females after grouping (in groups of 1 male with 7 females, 1 male with 4 females, or 1 male with 1 female) from 3 hours to 4 days. n = 8~12 for chaining behavior, and n = 12~24 for others. n refer to number of pairs or groups, housing conditions are indicated in the top of each panel (apply to all figures). Error bars indicate SEM. Please see Figure S1, Movies S1 and S2.