The effects of temperature, diurnal fluctuation and time of day on cecropin1 (CEC1) expression. (a) The amount of CEC1 in response to immune challenge (unmanipulated, black line; injury, blue line and heat-killed E. coli, red line) varied significantly depending on the average temperature mosquitoes experienced and the time of day challenge occurred (06.00, solid lines; 18.00, dashed lines). (b) Independent of immune challenge, the expression of CEC1 varied significantly with the mean ambient temperature a mosquito experiences, the time of day mosquitoes were placed into their temperature treatments (06.00, black lines; 18.00, red lines), and whether or not there was diurnal fluctuation (±0°C, solid lines; ±6°C, dashed lines). Asterisks denote significant differences of p < 0.05, and bars around population means represent standard errors.