As I was preparing to order our drosophila (fruit fly) cultures, I encountered a small problem. Carolina Lab would not ship their “Fly Nap” to a residential address. Fly Nap is their recommended way to temporarily knock out the flies for the students to examine them and separate them by sex or trait. They did sell a carbon dioxide system for drugging the flies, but it only came with 8 CO2 pellets, which probably wouldn’t have been enough, making it more expensive. I did some online research and found an easy and free way to knock out the flies.
Chilling fruit flies immobilizes them. They wake up quickly when returned to room temperature. We used a modification of the technique found at: http://ableweb.org/volumes/vol-24/mini.5.ratterman.pdf. This is what we did:
- Place an empty vial in ice for several minutes.
- Tap the vial containing flies to be transferred against a table to knock the flies to the bottom. Quickly unstop the vial and invert it over the chilled empty vial.
- Hold the two vials together and tap against the table until the flies have been knocked into the chilled vial. Replace stoppers.
- The chilled flies can then be dumped onto a plate that has been placed on top of a bowl of ice to chill. Flies will remain unconscious as long as they are on the chilled plate. Students can then examine them, sort them, and discard them into a morgue or place them in vials for new crosses.
This worked very well, eliminated all risks to students or flies by the use of ether or other chemicals and cost nothing. You can read more detailed procedures at: http://ableweb.org/volumes/vol-24/mini.5.ratterman.pdf.