Fig. 4. Mean ventilatory frequency at 20°C and 40°C, and the average change in frequency from 20°C to 40°C in each group. (A) There was a significant interaction between the effects of pre-treatment and sex on ventilatory rate at 20°C, which was driven by a significant difference between control and HS females. 16:8 control females had a significantly lower ventilatory rate at 20°C than 16:8 control males, 16:8 HS males, 16:8 HS females, and 12:12 HS females. (B) There were main effects of photoperiod and sex on ventilatory rate at 40°C. 16:8 control females had a significantly lower ventilatory rate at 40°C than 16:8 HS males, 12:12 control males, 12:12 HS males, and 12:12 control females. 16:8 HS females had a significantly lower ventilatory rate at 40°C than 12:12 HS males. (C) There was a main effect of photoperiod on the change in ventilatory frequency from 20 to 40°C, and there was a significant interaction between the effect of sex and pre-treatment, which was driven by a significant difference between HS males and females. 12:12 HS males had a significantly higher change in ventilatory rate from 20 to 40°C than 16:8 control males, 16:8 control females, 16:8 HS females, and 12:12 HS females. 12:12 control males and 12:12 control females had a significantly higher change in ventilatory rate from 20 to 40°C than 16:8 control females and 16:8 HS females. Error bars may be hidden behind symbols.