The extended feeding time response on cattle of adult lone star ticks, Amblyomma americanum (L.), during November through December is facultative and is mediated by the female. Mean feeding time (11.8 d) in female ticks taken from the field and held at 14:10 (L:D) photoperiod and 25 degrees C for greater than or equal to 15 d was significantly shorter (P = 0.05) than for females taken directly from the field and fed on cattle (14.6 d). Mean feeding times of females from the field paired to males from the field, males from the field held for 30 d at 14:10 (L:D) and 10 degrees C, or males from the field held for 30 d at 14:10 (L:D) and 25 degrees C were not significantly different (15.7, 16.3, and 16.2 d, respectively). When males from the field were paired with females from the field that had been held at 14:10 (L:D) and 10 degrees C or 14:10 (L:D) and 25 degrees C for 30 d, mean feeding time of the females was significantly longer (17.2 d) or shorter (14.0 d), respectively, than for all other groups.