Newly eclosed flies were kept at 25oC for 84hr. Aged, mated flies were transferred to empty glass vials and the temperature was decreased to 0oC at a rate of 0.2 degrees per minute; the flies were then held at 0oC for 9 hours. After the cold treatment flies were transferred to fresh food vials and kept at 2oC for a 2-hour recovery period. Flies were then flash frozen in liquid nitrogen and stored at -80oC prior to RNA preparations.