Why Won't My Millipedes Breed

Why Won't My Millipedes Breed? A Troubleshooting Guide

You've set up a nice enclosure, you've got a group of millipedes, conditions seem fine — and nothing's happening. No eggs, no tiny juveniles, no sign of a growing colony. It's one of the most common frustrations in the hobby, and the good news is that the causes are usually short, fixable, and well understood.

Millipede breeding isn't difficult once the conditions are right, but it's slow, and "slow" trips a lot of people up. Before you assume something's wrong, it's worth running through the genuine reasons a colony fails to reproduce. We'll go through them roughly in the order they tend to be the problem.

1. You haven't waited long enough

This is, by some distance, the most common reason — and it isn't really a problem at all.

Millipedes are slow. Many species take two to three years to reach sexual maturity, and even fast-maturing ones take many months. If you bought a group of juveniles six months ago, the most likely explanation for no breeding is simply that they're not adults yet.

It varies a lot by species. A Ghana Speckled Leg (Telodeinopus aoutii) reaches maturity at two to three years. An Amber Millipede (Pelmatojulus ligulatus) is around two years. At the other end, prolific species like the Thai Rainbow (Atopochetus spinimargo) and Hawaiian Glow (Spirobolellus sp. "Maui") can start reproducing from around ten to twelve months and then multiply quickly.

If you want a colony that produces sooner, that's worth knowing at the point of purchase — choose a prolific, fast-maturing species rather than a giant. But if you've already got slow-growing giants, patience genuinely is the answer.

2. Your substrate isn't good enough

If the timeline checks out and breeding still isn't happening, look at the substrate next. This is the single biggest controllable factor, because the substrate is both their food and their egg-laying medium.

Females need to be well-fed and in good condition to invest in eggs, and producing eggs is calorie-expensive. A substrate that's inert, exhausted, or nutritionally thin won't support reproduction even if the animals survive on it. Remember that millipedes eat their substrate — over time the leaf litter and rotting wood get consumed and the mix degrades into something more like plain soil. A colony living on spent substrate is a colony that won't breed.

The fix is to make sure the substrate stays rich in the things they actually eat: deciduous leaf litter and white-rotted hardwood, topped up regularly. Our leaf litter and shredded rotten wood are the dietary staples here, and flake soil makes a nutritious base. If you're not confident your mix is right, our complete millipede substrate guide walks through exactly what it should contain and how deep it needs to be.

Depth matters for breeding specifically: females lay eggs in chambers they construct down in the substrate, so shallow substrate gives them nowhere suitable to lay.

3. Not enough calcium or protein

Two nutritional shortfalls quietly suppress breeding.

Calcium. Breeding females have a much higher calcium demand than non-breeding animals, and a calcium-deficient colony struggles to reproduce — quite apart from the failed moults and weak exoskeletons that deficiency also causes. Calcium should be available at all times, not offered occasionally. Keep a piece of cuttlebone in the enclosure for grazing and mix crushed oyster shell through the substrate for a slow-release source.

Protein. Many species benefit from periodic protein, and breeding females in particular eat a lot when they're producing eggs. A little bee pollen — a hobby favourite for supporting reproduction — or some tropical fish flakes offered once or twice a week can make a noticeable difference, especially in slower-breeding species where every brood counts. Don't overdo it; remove uneaten food within a day or two to prevent mould.

4. Temperature is too low

Millipedes will survive at the cool end of their range, but survival and breeding aren't the same thing. Many tropical species simply won't reproduce reliably at typical UK room temperature, especially in winter.

A Ghana Speckled Leg, for instance, will tolerate 18–20°C but is on the cool side there — it wants 22–28°C to thrive and breed. The fix is gentle supplemental heating: a heat mat on a thermostat is usually enough to lift an enclosure into the right range during the colder months.

One critical detail, because getting it wrong kills millipedes: never put a heat mat underneath the enclosure. Millipedes burrow down to escape unfavourable conditions and to moult, and a mat underneath cooks them between the heat below and the drier surface above. Always mount the mat on the side of the enclosure, above the substrate line, or use overhead heating.

5. You're not simulating seasons

This is the one that experienced keepers reach for when everything else is right and breeding still isn't happening, particularly with species from regions that have distinct wet and dry seasons.

Several of the African species — the African Giant Chocolate (Ophistreptus guineensis) from the Ghanaian and Nigerian savannah is a good example — appear to use seasonal change as a breeding trigger. In the wild they experience a dry period followed by rain, and replicating that cycle can stimulate egg-laying.

The method: let the enclosure dry out a little for a few weeks (without ever letting it go bone dry, since they still need to feed), then increase misting and humidity to mimic the arrival of the wet season. That shift from dry to wet is often what flips the switch. The same approach helps with several Spirostreptids — a slight increase in temperature and misting frequency to imitate the wet season.

6. You can't see eggs and juveniles that are already there

Sometimes breeding is happening and you just haven't noticed — and worse, you might be destroying it during maintenance.

Millipede eggs and freshly-hatched juveniles are tiny and live down in the substrate, exactly where they're easily missed. If you're doing full substrate changes, there's a real chance you're throwing out eggs and young with the old material, or crushing a soft, moulting animal you couldn't see. This is why we always recommend topping substrate up rather than tearing it down. Spot-clean, add fresh leaf litter and wood, and leave the deeper substrate undisturbed. If you ever must dig through it, go slowly and check every handful.

And leave the young with the adults. In many species — Chocolate, Ghana Speckled Leg, Red Fire and others — juveniles feed on the adults' frass, which gives them the gut bacteria they need to digest their food properly. Separating them too early can set them back or kill them.

7. You've got the sexing wrong

If you bought a small group, it's entirely possible you simply don't have both sexes — or you've misjudged who's who.

Sexing Spirostreptid millipedes is reliable once you know what to look for. Males have the legs on the seventh body segment replaced by gonopods — specialised reproductive structures tucked into pouches, which make that segment look different or thicker than the surrounding ones. Females and immature animals have normal legs all the way along. The seventh segment is the place to check on any of the common giant species.

If after inspection you find you've got all one sex, that's your answer — and a reason to keep groups rather than singles, since it improves the odds of having a breeding pair.

A quick checklist

If your millipedes won't breed, work through these in order:

1. Are they actually adults yet? Most species need 1–3 years. This is usually it.
2. Is the substrate rich and deep? Topped up with leaf litter and rotting wood, deep enough to lay in.
3. Is calcium always available, and are you offering occasional protein?
4. Is the temperature in the species' breeding range, not just its survival range?
5. Have you tried a dry-then-wet seasonal cycle?
6. Are you accidentally destroying eggs and young during maintenance?
7. Do you definitely have both sexes?

Get those right and most species breed without any further intervention. If you're setting up specifically to breed, choosing a prolific species from the start makes everything easier — browse the millipedes for sale collection and look for the ones described as ready breeders, and have a look at our best millipedes for beginners guide for which species establish colonies most readily. As always, our live chat is happy to help you troubleshoot a specific setup.