African fruit beetles like Pachnoda marginata are some of the easiest tropical pet beetles to keep and breed in captivity. The adults grow to around 3cm in length, being an attractive combination of orange/yellow and brown. They’re reasonably active – especially when provided with suitable light and heat – so can make an attractive display species.
If I’m honest, though, I initially started keeping this as a feeder species, so that with very little effort on my part I could have a regular free supply of grubs for feeding to my tarantulas and day geckos. Since then, however, they’ve become an important part of my collection and have encouraged me to investigate keeping other species of beetle too.
If you’re looking to keep Pachnoda marginata – the most common fruit beetle in the hobby – then read on for my detailed care sheet…
Pachnoda marginata hails from a wide area over Africa. Here they are used to high temperatures and reasonable levels of humidity. They are commonly found on the forest floor.
Like many other beetles, the grubs spend most of their life below ground level, feeding on decaying plant matter such leaf litter, rotten wood and ripe fruit. After some months of development they will turn into a cocoon, before appearing soon afterward as an adult beetle.
While keeping fruit beetles on a substrate of leaf litter is most common in captivity, I did stumble across one interesting field study where Pachnoda marginata was found living in a bat cave in Ghana. The scientists in question found them living successfully among the guano that had been produced by the bats, and found that specific bacteria found in the fruit beetle’s gut allowed it to feed on this unusual food source.
Cages & Housing
Fruit beetles can be kept in a variety of different cages and can be both cheap and easy to accommodate as pets. For the best possible display consider one of the glass tanks built specifically for exotic pet keepers, such as Exo Terras or ReptiZoo terrariums.
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There are, however, a number of weaknesses to such cages, despite their amazing experience. Firstly, they don’t provide much depth of substrate – something which is considered important for Pachnoda marginata.
Additionally, there’s no denying that Exo Terras are far from cheap. For people on a budget, or who are planning to breed Pachnoda marginata as feeders, therefore some other options are suitable.
Firstly, some people opt to use an old fish tank, where adding a solid depth of substrate is easier. Note that adult fruit beetles have wings and can fly quite well, so if you opt to use a fish tank then be sure to add a tight-fitting lid. A number of mesh vivarium lids are currently available and make a worthy investment to prevent escape.
Another suitable option – and the one I’m personally using at the moment – is to make use of suitably-sized plastic containers. Whether you opt for a Kritter Keeper (which includes a decent mesh lid) or just a plastic box is entirely up to you.
- Rectangular Kritter Keepers have self-locking lids with hinged viewer/ feeder windows
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Right now I’m using plastic boxes of around 30cm long x 20cm wide x 30cm deep. These have close-fitting lids being sold for general household storage. I have used an electric drill to add ventilation holes around the top of the cage. This is probably the cheapest option of all, though admittedly doesn’t look anywhere near as good as a proper glass tank.
Giving an idea of what cage size Pachnoda marginata requires is difficult. On the one hand these are small beetles, so can potentially be kept in quite small cages. On the other hand, you’re likely to purchase a number of these rather active beetles to start your colony, so I would suggest a cage no smaller than 12” long. As your colony grows you may opt to split it into several colonies, or to rehouse your fruit beetles into a larger cage.
Once you’ve selected a suitable cage for your Pachnoda marginata fruit beetles there are a few extra things you’ll need to fit out the tank. The most important of these is the substrate.
As fruit beetle grubs feed on dead and decaying plant matter they should be provided with leaf litter, dead leaves and rotting wood on which to feed. Personally I have an area at the bottom of my garden with some trees, so it’s simple enough to gather up some leaf litter and fallen wood. This can then be mixed with more traditional exotic pet substrates like coconut fibre or potting compost (I have used both with success).
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Alternatively a small number of exotic pet retailers sell specially-prepared “beetle substrate” which, while more expensive, is equally as effective.
Experts disagree on the perfect depth of substrate that you should provide. Once again, I believe this will largely be determined by how many grubs you’re keeping in a single cage. A typical recommendation is at least 6” of substrate, but as the grubs don’t get overly large I’ve also had great results from a far shallower substrate depth closer to 3-4 inches.
While we’re talking about tank decor it is worth mentioning the value of wood. I find that the vast majority of my Pachnoda marginata grubs choose to attach their cocoon to the underside of flat pieces of wood.
I don’t know why this is, but it can make monitoring your cocoons quite easy – simply pull out the piece of wood, turn it over, and look at all the cocoons waiting to hatch. For this reason I now like to include a flat piece of corn bark on (or close to) the surface of the substrate.
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Temperature & Heating
Coming from tropical Africa, sun beetles appreciate a warm environment. The hotter they are kept – within reason – the more quickly they will develop. For tarantula keepers and reptile enthusiasts keeping Pachnoda marginata as a feeder animal, it therefore makes sense to keep them towards the top end of the scale.
For hobbyists, however, it may be more practical to keep your fruit beetles at a more modest temperature.
A good range of temperatures is somewhere between 20-25’C. My office, in which I house all my exotics, remains a constant 20-22’C year round thanks to the range of heaters present, so I personally don’t provide my Pachnoda marginata with any supplementary heating. If your home gets cold, or you want to speed up the development of your fruit beetles, then some supplementary heating may be advisable.
Probably the easiest option here is to use a low-powered heat mat. As the grubs burrow in substrate it is not a good idea to place the heater underneath the tank – as is typical with many exotic pets. Instead it is wiser to tape the heater to the outside back or one side of the tank. This will ensure that your beetles can move about and select the area that suits them best, as one area will be warmer than the others.
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As with any form of exotic pet heating it is advisable to use a thermostat to prevent the risk of overheating, especially in warmer weather.
Note that sun beetles are well-named, as the adults seem attracted to sunlight and will be far more active in brighter conditions. You’ll therefore want to make sure that your adult Pachnoda marginata are exposed to decent light for much of the day.
There are a number of ways to provide this requirement. The easiest option I have found is to place the fruit beetle cage on a north-facing windowsill. In this way they get maximum light, but without the risk of overheating in any direct sunlight.
Some of my other colonies have access to artificial light, being kept close to my day geckos, meaning day-long artificial light shines into their cage.
Water & Humidity
As a golden rule, I aim to provide a dish of water to all my exotics at all times so they can drink if they so choose. Sadly Pachnoda marginata makes this very difficult indeed, as you will find that the substrate is constantly moving. Anything placed on the surface of the substrate slowly disappears beneath the surface, making the provision of a waterbowl almost pointless.
Instead, I let my beetles absorb the moisture they need from their food.
One area where moisture and humidity is important relates to the substrate itself. You should aim to keep the substrate moist but not wet. This may involve regularly spraying the cage with a houseplant spray gun.
Note that a stale, stuffy environment should be avoided, so good ventilation is important. Experiment over time with a combination of ventilation and spraying until you find the right routine to maintain a moist substrate but without any mould or fungi building up.
The feeding of Pachnoda marginata can be separated into their two key life stages – the subterranean grubs and the sun-loving adult beetles.
As discussed, the grubs will feed almost entirely on rotting leaves and wood. This means that once your tank is set up for the first time very little ongoing feeding is necessary. Simply keep an eye on the proportion of leaves and wood present in the cage and top up occasionally as necessary to offer a constant supply.
Adult fruit beetles, as their name suggests, feed primary on very ripe fruit. Scientific studies have found that they can recognise dozens of different fruits based on their scent alone. Any soft, sugary fruit such as banana, melon, citrus or mango is suitable for the adult beetles.
Interestingly, the grubs will also sometimes feed on such foods, dragging them slowly under the substrate. Of course, great attention should be paid to hygiene, lest your Pachnoda marginata cage starts to smell of rotten fruit over time.
Another option, which is cheap, easy and very practical, is to make use of jelly pots sold specially for beetle keepers and breeders. Simply tear the lid off and place it on the surface of the substrate so your adult beetles can feed.
If you “pop” the entire jelly out of the pot and leave it loose on the surface of the substrate you will normally find that your active grubs gently drag it down into the substrate and eat it out of sight.
Pachnoda marginata can be handled without too many issues. These beetles tend to be quite docile, and unlike some other pet beetles they don’t any unpleasant projections that can do you any serious damage. That said, appreciate that they can fly, so try to only handle them in an enclosed room.
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