Fruit fly cultures are often bred for specific purposes, such as feeding pet reptiles or amphibians. Producing a lot of fruit flies of therefore one of the main goals of a fruit fly culture.
There are several factors that can regulate or even limit fruit fly production in a culture. Those are temperature, humidity, mold, overpopulation, mites, and of course, the type of media used.
Each of these factors can limit fruit fly production.
The desired temperature for fruit fly cultures is between 70 and 80° F (approx. 21 to 26,7° C). They also don’t like direct sunlight and this can heat up a plastic cup very quickly.
Temperatures below 70° F will lead to slower production.
When the temperature is around 60° F (approx. 15,6° C), the fruit flies lifespan decreases, and with temperatures below 53° F (approx. 11,7° C), the fruit flies will stop developing. Fruit flies won’t die from a short temperature drop, but it obviously won’t help you to increase production.
Some fruit fly breeders cool their colonies down in the fridge for a few minutes before feeding them, because cooling them down will disable them to fly, which makes it way easier to feed them to other pets. If you own flightless fruit flies, this is not necessary, since your flies cannot fly anyways.
Temperatures above 85° F (approx. 29,5° C) can make the fruit flies go sterile and they won’t be able to produce a new generation.
Fruit flies prefer higher humidity. While the normal humidity level in a household is usually between 30% and 50%, fruit flies need a humidity of 60% – 80%.
Common plastic containers, in which fruit fly cultures are usually bred, are a great way to keep the humidity inside which is good for the fruit flies.
Humidity below 65% can dry the media out which will eventually kill the fruit fly culture.
The humidity in a fruit fly culture can be increased by regularly spraying some water into the culture. It is also possible to keep your cultures in the bathroom, where the humidity is usually higher than in the rest of the house due to showering.
The humidity should not be too high either, because it promotes mold.
You can check the pupae in the culture to find out if the humidity level is good or needs to be adapted. If you see most of the pupae concentrating closer to the media at the bottom, the humidity might be too low. If the majority of pupae is more on the top of the cup, the humidity is probably too high.
Fruit flies do not like a high levels of CO2. In fact, they will try to avoid places where the CO2 level is even a little higher than usual. But when they are bred in a culture, it is hard to escape, and therefore it is your job as a breeder to keep track of the population to avoid a higher CO2 level which can kill your fruit flies.
And this is how the CO2 level increases: Overpopulation can lead to stressed fruit flies. And stressed fruit flies produce CO2. CO2 also results from fermenting food, so depending on what you feed your fruit flies, the food might also increase the CO2 level.
The solution is to regularly remove fruit flies from your population if you notice that there are more flies than usual.
Mites can be a problem to fruit fly cultures and they can be quite a threat when they spread.
Some mites, such as the very common white grain mites, are in all grains and very common in fruit fly cultures. Usually, they are not a big problem, as long as the flies are doing well. If the flies are already suffering, the mites might take over the power in the culture, which you want to avoid, if you don’t want to lose your fruit fly culture.
Other mites are more aggressive and will not only eat the fruit flies food, but rather the embryos and pupae of your fruit flies which will quickly end your colony.
Here are ways how to control mites in your cultures
If you detect any mites in your culture, try to feed as many of the flies as you can and toss the rest.
Do not use the flies to create a new culture, otherwise, you will spread the mites.
You can store the media (before you use them for your fruit flies) in the freezer. This will prevent mites.
If you keep your flies together in one big culture, make sure to quarantine incoming flies before letting them join your existing stocks.
You should also transfer your fruit flys regularly to new, clean cups. Most mites have a life cycle that is a bit longer than one of your flies, and removing the fruit flies will also remove the mites’ food base.
Don’t mix flies from different cultures to create a new culture to prevent any mites from spreading.
If you detect mites on any equipment that you want to keep using, make sure to disinfect everything properly with ethanol as this kills the mites.
Fruit flies need food to survive. Fruit fly cultures that are bred at home can either be fed through a commercial or self-made media, or also simply fermenting fruits, plants, and vegetables.
Even though they can go for up to seven days in starvation, they will start to die off after about 4 to 5 days without food.