Feeding millipedes is straightforward once you understand what they are: detritivores. They eat dead and decaying plant matter. That's their ecological role in the wild, and it doesn't change in captivity. The trick is making sure they get everything they need from what you provide, because a millipede diet that's missing calcium or variety will cause problems over time.
The staple: rotting wood and leaf litter
This is the foundation of any millipede diet, and for many keepers, it's the part that gets overlooked. The substrate in your millipede's enclosure isn't just bedding. It's food. Millipedes graze on decaying hardwood and leaf litter more or less constantly, and for large species like Archispirostreptus gigas, the substrate is their primary food source.
Use well-rotted deciduous hardwood. Oak, beech, and birch are all good choices. The wood should be soft enough that you can crumble it between your fingers. If it's still hard, it hasn't decomposed enough. Avoid all softwoods: pine, cedar, spruce, and any coniferous wood. The phenols and terpenes in softwoods are toxic to millipedes and can be fatal.
Leaf litter is equally important. Dried oak and beech leaves should be scattered thickly over the substrate surface. The millipedes will gradually consume them, so top them up regularly. You can collect leaves from parks and woodland, though avoid areas that may have been treated with pesticides or herbicides. Roadsides are not ideal collection spots either, due to vehicle exhaust contamination.
Fresh vegetables and fruit
On top of the substrate-based diet, millipedes enjoy fresh produce. Vegetables are better than fruit as a regular supplement because they're less sugary and less likely to attract grain mites.
Good vegetables include cucumber, courgette, butternut squash, sweet potato (raw or lightly boiled), carrot, and mushrooms. Place a piece on the substrate surface and the millipedes will find it. Replace it every two to three days before it moulds.
Fruit can be offered occasionally. Banana is a favourite for most species, and apple slices go down well too. Don't overdo it, though. Fruit rots quickly in warm, humid enclosures and can cause a spike in grain mite numbers if left in too long.
One thing to watch: avoid avocado, as it's toxic to many invertebrates. Citrus is also best avoided. The acidity doesn't agree with most millipede species.
Calcium
This is the one thing you absolutely cannot skip. Millipede exoskeletons contain calcium carbonate, and they need a constant supply of dietary calcium to build and maintain them. Without it, moults fail, exoskeletons stay soft, and the millipede eventually dies.
The easiest calcium source is cuttlefish bone. Leave a piece in the enclosure permanently and replace it when it's been gnawed down. You'll often see your millipedes rasping at it, particularly after a moult when calcium demand is highest.
Other calcium sources include crushed eggshell (baked first to sterilise), calcium carbonate powder dusted over food, and crushed oyster shell mixed into the substrate. Some keepers use limestone chips in the substrate as a slow-release calcium source, which works well.
Protein
Millipedes aren't primarily protein eaters, but they do seem to benefit from small amounts. In the wild, they'll encounter animal matter incidentally while feeding on decaying material. In captivity, some keepers offer dried shrimp, fish flake, or a smear of plain, unsweetened yoghurt on a piece of bark.
Keep protein supplementation occasional and in small quantities. Overfeeding protein can contribute to mite problems, and millipedes don't need much. Once a week, a small amount is more than enough.
What not to feed
- Softwood of any kind (pine, cedar, spruce). Toxic.
- Avocado. Toxic to many invertebrates.
- Citrus fruits. Too acidic for most millipede species.
- Anything treated with pesticides or herbicides. This includes most shop-bought salad unless it's organic, and even then, wash it first.
- Commercially treated or painted wood. The chemicals leach into the substrate.
How much and how often
Millipedes graze continuously, so there should always be food available. The leaf litter and rotting wood in the substrate handle this for the most part. Fresh vegetables can be offered two or three times a week. Remove uneaten veg before it goes mouldy.
You'll find that consumption varies. After a moult, millipedes tend to eat more as they rebuild their exoskeleton. In cooler conditions, they eat less. If food is going untouched, reduce the amount or change what you're offering. Millipedes can be surprisingly fussy about individual foods while happily eating others.
Substrate as food: getting it right
Because the substrate doubles as a food source, it needs to be replenished as it gets consumed. Over months, you'll notice the substrate level dropping as the organic material is eaten and broken down. Top it up with fresh rotting hardwood, leaf litter, and a sprinkling of calcium. Don't replace the entire substrate at once, as this removes the beneficial microbial community that helps break down organic matter for the millipedes.
A good substrate mix for millipedes is roughly 50% well-rotted deciduous hardwood, 30% coco coir for moisture retention, and 20% organic topsoil or leaf mould. Mix in some cuttlefish bone fragments or calcium powder, and keep it damp throughout.
If you get the substrate right and keep calcium available, feeding millipedes is one of the least demanding parts of keeping them. They mostly feed themselves.