Some Helpful Hints and Tips to get your Flies through the Cold

Introduction

Fruit Flies (Drosophila sp.) are one of the most popular feeder insects for those animals that require smaller prey items, such as poison dart frogs. Unfortunately, these typically easy to culture insects often encounter difficulties with colder weather. This blog entry will address the most common issues, and what to do about them.

Shipping

The reduced temperatures winter brings makes shipping live animals even more difficult than it already is, and shipping fruit flies are no exception. At Josh’s Frogs, we ship using styrofoam lined boxes and with heat packs when the temperature drops, but even so, the interior temperature of a package can vary widely in transit, depending on how it is handled by the carrier, and the length of it’s travels.

During winter, Josh’s Frogs ships using styrofoam lined boxes with heat packs.

In a styrofoam lined box, a fruit fly culture will maintain interior temperatures approximately 10 degrees above that of it’s surroundings. Adding a heat pack will raise the temperatures another 10 degrees. Even at 20 degrees above ambient temperature, the cultures will experience a wide range of temperatures in transit, due to the change in the daytime highs and overnight lows the part of the country the package passes through experiences. This constant temperature shift certainly does not have a positive effect on the fruit fly cultures – at best, it has a neutral effect, and often negatively impacts the culture. It’s very easy for cold weather to slow down or stop the natural progression of a fruit fly culture during shipping. Often, it delays peak production by several days – that is why producing cultures sometimes take a few days to catch up after shipping in winter. If the fruit fly culture is exposed to very cold temperatures, flies, pupae, and/or larvae may perish. Once situated in a proper environment the culture will rebound, but sometimes chilly weather may cause the culture to fail, and/or allow grain mites to exponentially reproduce in the culture, leading to it’s demise.

Temperature

Average house temperature during the winter is substantially less across the United States. Lower temperatures will not necessarily result in less fruit flies produced per culture, but can greatly increase the length of time it takes a culture to produce flies. Accompanying the delay in fly production is an increased threat of grain mites – these pests are capable of reproducing in a much wider range of conditions than fruit flies are. Grain mites are present in all fruit fly cultures, and in most situations are not harmful, but if given the proper conditions, they are capable of overrunning a fruit fly culture, and eventually crashing it. Typically, if the temperature is increased to a level more favorable for fruit flies, they will resume production, and the mites themselves will be out competed.

There are several ways to insure that fruit flies receive the required temperatures during the winter (ideally as close to 78F as possible). The easiest method is to keep the fruit flies near a heat source, such as a water heater or lights used to light the animal enclosures. When trying this, remember that heat rises, and often cultures located nearer the ceiling of a room will be several degrees warmer than ones located near the floor. Alternatively, creating an incubator of sorts for the cultures can keep them warm. Anything from reptile egg incubators to a plastic container with a heat source, such as a basking bulb or heat pad, can be effective.

Humidity

The cold winter weather generally leads to the furnace running most of the time. This not only increases the household temperature, but also substantially decreases the relative humidity. Ideally, fruit fly cultures are maintained at 60-80% humidity, and lower humidity can result in the culture media drying out, allowing a ‘skin’ to form over the surface of the media (just like pudding can form a ‘skin’ if left in the fridge). This ‘skin’ will suffocate the larvae, or cause them to climb up the sides of the culture in search of oxygen. Spraying the culture with a bit of water will correct this issue.

Under ideal humidity, fruit fly pupae should be concentrated around the mid level of a culture.

By looking at the placement of pupae on the side of a culture, you can infer if the culture is receiving the proper humidity or not. Under ideal conditions, the pupae will be spread evenly throughout the sides of the culture, with most of them located at mid level. If most of the pupae are located at the top of the culture, the humidity is too high. If the pupae seem concentrated lower in the culture, towards the media, the humidity is too low. Keeping cultures in plastic storage drawers, such as those made by Sterilite, is a quick and easy way to insure that proper humidity is maintained.

Conclusion

Winter poses many challenges to the proper production of fruit flies. Using the hints and tips outlined in this blog post, most problems can be solved quickly, and plenty of fruit flies can be produced for your herps.

Fruit flies are one of the easiest feeder insects to care for. Each 32 oz fruit fly culture includes all the food and water the flies will need for months. The culture will continue to produce flies for at least 2 months. Freshly Started Hydei Cultures will start to produce flies you can feed to your animals in 17-21 days. Freshly Started Melanogaster Cultures will start producing flies in 10-14 days. Each culture has the potential to produce 1000s of flies, but there are a few things that can slow down or stop production all together.

Humidity

Fruit fly cultures are prone to dry out in environments that are under 65% humidity. To maintain humidity, place the culture inside of a clear Rubbermaid container or storage shelving unit to keep the culture from drying out. You can also spray down the culture with de-chlorinated water if it dries out.

Temperature

Fruit fly cultures should be kept between 70 and 80 degrees. If the cultures hit 85 degrees even for a little while, the culture will go sterile and will not produce any more flies. Cultures that are kept under 70 degrees produce much slower.

Mold

Our 32 oz fruit fly cultures are made with a media that has a mold inhibitor already in it. However, if the culture begins to dry out, mold will appear on the top of the media. If mold develops on the top of the media, spray the mold down with some de-chlorinated water and put the culture in a clear Rubbermaid container or storage shelving unit to maintain humidity.

Mold will occasionally develop on the coffee filters or excelsior used in the culture. To prevent this from happening, make sure cultures are away from heater/air conditioner vents. If mold develops on the coffee filters or excelsior used in the culture, remove the portion with the mold on it before starting new cultures from that culture to avoid spreading the mold. Feeding from a moldy culture will not hurt your animals.

Mites

Mites are tiny bugs that love to attack fruit fly cultures. Mites are everywhere, so care must be taken to prevent mites from taking over your cultures. All cultures should be placed on paper towels that are sprayed with a Mite Spray. In addition, the area where the fruit flies are stored should be cleaned regularly.

If mites attack your cultures, it is best to toss all of your cultures and buy new fresh cultures.

Making Fruit Fly Cultures

Supplies:

1. Fruit Fly container and lid

2. Fruit Fly medium

3. Water free from Chlorine – Chlorine will slow the rate of fruit fly production. You can use distilled, RO, spring, etc.

4. Active Baker’s Yeast

5. Coffee Filters or Excelsior - Needed to create more surface area for more flies.

Procedure

The biggest (and most would argue only) drawback to keeping Dart Frogs is escaped fruit flies. There is nothing worse than feeling a fruit fly crawl over your arm or hear your guests comment on the amount of bugs in your house. There is, however, no reason for your house to be crawling with fruit flies no matter how large or small your Dart Frog collection is. Here is a list of a few things I do to keep down on loose fruit flies.

There is nothing worse than dropping a cup full of fruit flies and have them spill all over your floor. Keep a vacuum or shop vac near your tanks. If you have never dropped a cup of flies, don’t worry. You will someday.

Every time you feed your frogs your flies will make a quick dash towards your light and out every crack, vent, and crevice in your tank. For this reason, I have no vents on any of my tanks (they get air flow when I open them up every day). I also seal the none moving parts of my lids with silicon to keep flies from escaping (especially the aquarium lids that have the plastic back).

I also keep a glass of apple vinegar in my frogroom. The flies flock to this cup and quickly drown. I don’t like the smell of vinegar, so I only put an inch or so of it in the corner and change it weekly.

Finally, I allow free-roaming spiders to set-up webs by my tanks. I wipe away any webs that get in my viewing area, but I allow them to create webs out of plain sight.
If these steps are taken, you will find that you rarely (if ever) see any free-roaming fruit flies. Do you have any methods that I haven’t listed? If so, please shoot me a comment with your techniques.