Fruit Flies, Fungus Gnats, Phorid flies and What to do About Them
Perhaps the most irritating pests when keeping captive animals are variety of flies. Like other pest animals, they are harmless but creepy, and really, really annoying. Who wants flies buzzing around their face, phone, and headlamp? There are some methods to handle these animals, thankfully. This article will discuss the most common pest fly species that are attracted to animal enclosures and how to eliminate them. Please keep in mind, this article uses common names and these common names may apply to a wide range of scientific terminology encompassing hundreds of species.
Fly populations will boom with the initial setup of an enclosure, because there are no other animals competing with the flies for resources. Establishing a healthy isopod and springtail population in any setup with dirt will discourage a large fly population. Some of the more predatory isopods will eat fly larvae, and springtails consume the same food sources that fly maggots do.
So, let’s talk a little bit about these animals and what they are. The fly that people are typically most familiar with are fruit flies. Fruit flies are a chubbier fly, and typically have a red body and reddish eyes. They readily appear when there are rotting vegetables or decaying fruits. In a household, they are easily removed when the source of their food is also removed. For isopod or gecko cultures, they are usually attracted to uneaten food that has decayed, so removing uneaten food and disposing of it outside will usually get rid of the problem.
Fungus gnats are a little trickier – they feed on bacteria, mold, and breed in stagnant water. People who keep a lot of plants are usually familiar with them, and the best method is to allow the substrate to dry out a bit. They are a small, black fly and are very attracted to light sources. Probably the most irritating part about this fly is that when they like a setup, they REALLY like it. They are particularly attracted to setups that have been freshly set up and will leave in a disgusting swarm when the lid is opened.
Phorid flies are regarded as the most difficult fly to remove. They are remarkably similar to fruit flies with one key difference: they typically infest and breed in drainpipes. They will also breed in dirt like fungus gnats, but pipes are their favorite place to infest. The best method to remove a breeding population of phorid flies is to clean pipes with a stiff metal brush, then flush the organic material down the pipes. Cleaning floor drains can be particularly tricky due to the amount of organic material and may require assistance from a professional company.
All flies have 3 life stages: larvae, pupae, and adult fly. Kind of like butterflies, but the horror version. All fly larvae are some form of maggot. There are the classic thick maggots of the larger house flies everyone knows that eat animal carcasses, but what many people don’t know is that the smaller fly species have maggots that look like small white worms. These maggots may be mistaken for nematodes, grindle worms, or even some parasites. Maggots are identifiable by small feet along the underside of the body, and black eyes at the front of the head. All maggots then turn into pupae, which then hatches into an adult fly. Pupae of smaller fly species look similar to small seeds.
Besides the specific methods we’ve discussed to eliminate these flies, there are additional methods that can be done to discourage the population. The most popular is a pest control product called Mosquito Dunks. This was specifically formulated to attack mosquitoes but works for a variety of flies as well. It’s an incredibly unique system, and very clever because it doesn’t harm other animals (although I have not tested it on reptiles and amphibians, so use with caution, either removing the animal from the setup for 48 hours or not spraying directly). Mosquito Dunks contain a bacteria called Bacillus thuringiensis israelensis, or B.T.I., which specifically targets the digestive system of fly larvae, causing them to starve to death. Since this targets the larvae specifically, it may take a few treatments to rid an infestation completely, as the adults can live as long as 3 weeks in some species. Mosquito Dunks are sold as a large puck that dissolves into water. The best method for using them in the home on cultures is to pulverize the Mosquito Dunks and dissolve it into water, then using the water to spray onto cultures. It will take several treatments to kill the flies completely, since it only kills the larval stage of the life cycle, and the adults will continue to lay eggs until the end of their cycle (about 3 weeks). One puck can treat 100sq feet of surface area of water. We typically crumble half a puck into every 8L of water sprayed.
Katchy, DynaTrap, and other UVB fly fan traps are an option for reducing fly populations. While they do not eradicate a population completely, but they are effective at killing breeding adults and keep them in check. These traps have a UVB bulb on top of the machine, and a fan that spins below. The bulb attracts and pulls in adults, and the fan pulls the flies down in a compartment to trap them. They are either killed by the blades of the fan or are kept trapped by air pressure until they dry out. This is a very safe method for a home with animals or children, because the bulb does not electrocute or get hot enough to burn, and the fan blades are made from a thin weak plastic that won’t hurt larger animals. Some of these fan traps even come with a replaceable sticky pad to collect the flies on. The rad part about the sticky pad is the gnats adhere to it and it is easy to see how many are collected, the downside is the pads fill up really fast if the infestation is bad. The good news is the fan traps work well without the sticky pads, but should only be emptied weekly to ensure the trapped flies have dessicated. UVB fan traps have a narrow opening, and typically only trap very small flies like fungus gnats.
There are additional UVB traps that have a wide top opening and are mounted on the wall. These traps have a sticky pad at the bottom to catch flies, and are safe as they don't electrocute the flies. Due to the wide opening, the trap can catch a wide variety of flighted insects including large house flies, moths, beetles, and other pests. The downside of this trap is it only works with the sticky pad, and it does fill up very fast.
A simple DIY trap that can be made is one with apple cider vinegar. These traps are made by placing apple cider in the bottom of a plastic cup, covering it tightly with saran wrap, and poking holes through the top. The adult flies crawl in through the holes, then either drown or die of starvation because they are unable to escape. To achieve best results, the vinegar should be replaced monthly, as the freshest smell attracts the most flies. If left unattended for too long, the flies may breed inside of the container and emptying it out is not a fun task. There are more aesthetic reusable traps that can be purchased online, and even fluid attractant that is several times more effective than apple cider vinegar. The purchased traps are hardy, and easy to use. They are simple to clean and the top and bottom unscrew, making it easy to put fresh bait in the trap. Apple cider traps work on both fungus gnats and fruit flies.
Yellow sticky traps are yet another method to trap and kill adult flies. There is a certain degree of risk with these traps because they are so sticky and strong they can trap other invertebrates, reptiles, and even small mammals. The bright, yellow color stimulates breeding receptors and brings in the adults, while the sticky adhesive keeps them from leaving. It’s not unusual for a female to be trapped, and then a male to be trapped while attempting to breed (euw). These can catch and kill a large number of flies but are visually unappealing and can stain surfaces with old adhesive. Plus, it really sucks if you accidentally touch or step on one. In the unfortunate scenario the trap catches an animal or is stuck to a shoe, the safest way to remove the trap is with either canola oil or olive oil. The oil should not be left on a reptile’s skin and should be gently rinsed off with cool water and patted down with a paper towel. It is worth noting that the yellow sticky traps do not lure in phorid flies, but they do work well on fungus gnats and fruit flies.
If flies are flocking around a sink or drain area, the problem is organic matter in the pipes. This lump of whatever it is will form a bio film, protecting it from many treatments. This biofilm protects existing fly eggs, and makes it extremely difficult to remove. Several DIY methods are described to help rid of the flies in these scenarios; some say to dump a mix of bleach and hot water, some say vinegar and baking soda, and others say hot water is enough. Pouring something down the drain won't dislodge the organic matter, and unless the food source for these flies is removed, they won't go away. The most efficient method to remove their food source is a firm bristled drain brush. These brushed have a long, flexible handle and can reach the majority of the drain, and dislodge the food source for these flies. Once the substance is removed, the adults either leave or die off very quickly.
A method that keepers often ask about is using predatory mites to control populations. Predatory mites are readily available online and used in agriculture to control soft bodied invertebrates like aphids plaguing crops. Predatory mites are a bit controversial, and we don’t recommend using them in a captive setting. They will prey on the fly larvae; but also, on springtails and other small invertebrates that may be present. The mites will die off without a strong enough food source, and the flies can easily make a comeback. Plus, mites are also super creepy, and we have an entire article dedicated to getting rid of them.
There are also commercial chemical treatments available to kill fly populations, but we can’t recommend any of these specifically since they will certainly kill or harm any animals also in the vicinity. If none of the methods discussed are working effectively, a local pest control company will typically offer a consultation to remove the pests, and are typically understanding of wanted animals, whether they have a spine or not.
Hopefully, the methods discussed in this article alleviate some stress when it comes to a fly infestation. While they are harmless, that doesn’t mean they aren’t awful.