It’s important to clean fly behavior equipment because flies leave feces and cuticular hydrocarbons on the behavior arena surface, and this can affect fly behavior. However, flies have a sensitive sense of smell, and can easily pick up on solvents used to clean behavior equipment. They can also sense if the surface is more or less slippery than it was previously. So, what are the best methods for cleaning fly behavior equipment?
First, you need to know what materials were used to construct your behavior arena. Second, you need to check what type of cleaning products are not compatible with that material. These days, most behavior arenas are made out of plastics like acrylics - this means you need to be very careful when using anything other than just water to clean the arenas. If your arenas are made out of glass or metal, you have a bit more flexibility but still want to check compatibility with soaps and solvents.
The most preferred method is to use just plain old water. If your tap water is really hard (ie high in dissolved minerals like magnesium and calcium) or sulphuric, then use distilled water. I don’t think there is a need to use double-distilled water. Basically, you hold the part of your behavior equipment that the flies behave in under running water then wipe with a kimwipe to dry. This also means that you need a way to take your behavior arenas apart because when you hold a closed system under running water, you get water buildup and it takes forever for the excess humidity in the arena to clear out. That is why we use systems made out of smooth plastics (ie not 3D printed plastics) and with sliding lids. Check out details on this in ‘What materials should I use for building behavior arenas’ and ‘What are the best dimensions for a behavior arena?’
The downside to using just running water is that there’s a possibility it won’t be able to get residual feces and cuticular hydrocarbons off of the (typically plastic) arena surface. We have typically used a trial-and-error method of first just using water and seeing if that works. If we suspect that water is not working well to clean that arena and the flies are gathering in certain places that might be marked by residues left from the previous flies in the arena, then we try an eco-friendly soap or a solvent and rinse really well after.
If plain water doesn’t work, soak equipment in water with a gentle, unscented soap after use, then rinse very, very well. Soap can leave a filmy residue on the equipment, especially if you are using any type of plastic, so it’s really important to rinse very well. Make sure to use a soap that doesn’t have any scent and is less caustic than most soaps. We use ‘Seventh Generation Dish Soap’ when we need to use soap (for example to clear out mineral oil from glass bubblers) because it’s a plant-based product that doesn’t use fragrances, dyes, phosphates, or triclosan. We don’t use soap with the plastic arenas that flies behave in because we have found that rinsing very well in distilled water works fine. If you can avoid it, try not to use regular dish or hand soap.
If just water doesn’t work, and gentle soap doesn’t work, you probably want to consider using a solvent. 70% ethanol is a common solvent used to clean bench surfaces in the lab. This can work for some behavior equipment (like glass or metal), but make sure to leave it dry a long time until the smell has worn off because the smell of even very low concentrations of ethanol can affect fly behavior. If you are using acrylic arenas, do not use ethanol because it dries the acrylic surface and they can get bumpy and crack. The same is true for all other alcohols used as solvents for cleaning.
Cuticular hydrocarbons can easily be cleared out using hexane. But, it can create problems with plastics similar to ethanol, resulting in dryness, deformations and cracks. If you feel you need to use hexane, make sure the materials your apparatus is made of is safe to use with hexane (ie not acrylic or any other type of plastic).
How do you find whether the cleaning agent you want to use is chemically compatible with your behavior equipment material? The good news is that chemists know this kind of stuff and you just need to check a chemical compatibility chart.
One of our favorites is a Chemical Compatibility Chart from Graco, Inc. It has a comprehensive list of solvents and lists whether they are ok to use with common metals, plastics, elastomers and leather.
Another of our favorites is a Chemical Resistance Chart from Plastics International. They list most plastics you would consider using to make behavior arenas, and a huge list of solvents that are or are not compatible.