The tiny, innocuous fruit fly has been a subject of research for more than a century, and is discussed in upwards of 100,000 scientific publications. Its surprising parallels with humans—the fruit fly has a beating heart, a brain, and other organs comparable to our own; exhibits complex behaviors including sleep and aggression; and slows down with age—have made it an ideal subject for research that’s furthered our understanding of biology, health, and disease. In First in Fly: Drosophila Research and Biological Discovery, Stephanie Elizabeth Mohr celebrates the power and importance of curiosity-driven pure research conducted with fruit flies, providing historic and contemporary examples of the profound knowledge such work has afforded. After First in Fly, readers will have a new appreciation for the beauty of the fruit fly, and the common genetic threads that connect us to other creatures. And yet, for many of us, that recognition won’t likely dislodge the lived experience of the fruit fly as a miraculously multiplying kitchen nuisance. For that, Mohr offers up the flytrap described below.
Although researchers take great care to contain fruit flies in a lab setting, some inevitably get free, and once free, the flies will follow enticing scents to places they are unwelcome, such as a lunchroom or a yeast research lab. Drosophila researchers are not likely to bring insecticides into the lab—we are for the most part trying very hard to keep fruit flies alive, after all, so that we can perform genetic crosses and do other types of studies. But even the most dedicated fly researchers recognize that rogue flies can be a nuisance. We have developed an effective strategy for capturing flies that have escaped from their culture vials: we place simple flytraps in strategic locations around the lab. The same approach can be used in a home to get rid of an unwanted infestation or to collect wild flies for study. In the 2014 BioSCAN project, volunteers in Los Angeles, California, placed flytraps in their backyards as part of a species survey. These backyard collections led to identification of several new species of phorid flies, as well as the observation that Drosophila flavohirta, a species not previously found in the Americas, has taken up residence in Los Angeles.
To make a trap, first gather the following: an empty bottle, a rubber band or tape, and a tablespoon of something attractive to the flies, such as fruit juice, cider, champagne, wine, red wine vinegar, mushy banana, tired grapes, or overripe mango. The materials should be assembled as shown, then placed in areas frequented by the flies. The paper cone or a similar cover with a single small opening is essential: an open jar constitutes a fly feeder rather than a flytrap. The opening in the paper cone or cover should be just large enough for the small flies to fit through. Flies will be attracted by the bait and enter the chamber. Once inside, they are unlikely to try to escape, and even if they try, it will be next to impossible for them to find the tiny hole through which they entered.
This is a live trap method. To get rid of the flies, seal and throw away the trap within a few days. If forgotten, the trap is likely to become the birthplace of a next generation of flies. Before tossing the trap out, the curious might examine the flies to determine what species of flies were caught and whether they have unusual or interesting attributes. Should you decide to culture the flies, sliced bananas with a sprinkle of baker’s yeast should suffice as a food source, and a piece of cloth secured with a rubber band or a plug of cotton can be used to stopper the top without depriving the flies of oxygen. Be careful not to let the food dry out or expose the flies to prolonged heat or cold. To anesthetize the flies for close examination, place the trap on ice for five to ten minutes. If the food is very mushy, put the trap on its side, so the anesthetized flies do not get stuck in the food, or use a funnel to transfer the flies to an empty bottle before placing them on ice. A small paintbrush, makeup brush, or crab pick can be used as a pusher, and a magnifying glass, macro lens attachment on a camera, or smartphone-compatible microscope can help you inspect your flies closely. Further information, including food recipes and video demonstrations, can be found online. Who knows? Isolation of a spontaneous mutation, observation of an interesting behavior, or some other chance finding might launch a groundbreaking study.