Anaesthetized adults were placed in a 15ml conical tube, flash frozen in liquid nitrogen, then shaken vigorously for 10 seconds. Broken flies were placed on a Petri dish on dry ice and frozen severed heads were removed with forceps to a fresh tube. Flies were processed in groups of 100 animals per dissection. Typically, heads were missing the antennal and maxillary organs, while the mouth-parts were retained.
