If your millipede has disappeared into the substrate, that can be completely normal. Millipedes often bury themselves to rest or hide, and they may also do so before a moult. Burial on its own is not proof that moulting is happening.

Why millipedes bury themselves

Burying is part of normal millipede behaviour. In the wild, many species live under leaf litter, rotting wood and the upper layers of soil, so spending time below the surface is what they are adapted to do.

There are three common reasons a millipede may bury itself:

• Resting or hiding: some species are naturally secretive and spend long periods out of sight.
• Premoult behaviour: a millipede may burrow deeper or stay hidden as it prepares to moult.
• Species differences: some millipedes are simply more buried than others, even when they are not moulting.

When a moult is approaching, the millipede is especially vulnerable. Its old exoskeleton has to split and be shed, and the new body underneath is soft at first, so being underground gives it privacy and protection.

What buried behaviour usually means

Buried behaviour by itself usually means nothing is wrong. A millipede that disappears for a day or two, or even longer, may just be resting or behaving naturally. That is why digging one up without a clear reason is usually unnecessary and can be stressful, especially if it is preparing to moult.

If you want to judge what is happening, look at the whole picture rather than the fact that the millipede is underground. The most useful clues are how it has been behaving overall, how long it has been hidden and whether it is showing any signs of premoult.

Signs it may be premoult: reduced activity, spending more time underground, less interest in food, a fuller or slightly duller-looking body, and a general shift towards staying hidden. These signs can suggest a moult is approaching, but they do not confirm it on their own.

Useful context

After moulting, a millipede may stay underground for a while as the new exoskeleton hardens, so you still might not see it straight away. Different species also vary: some are often visible on the surface, while others are rarely seen except when feeding or during enclosure maintenance.

If you want the broader picture of the moulting process, see our Millipede Breeding, Moulting & Lifecycle Guide or browse the Millipede Breeding & Lifecycle Guides hub. If you are deciding whether to act now, read Should You Dig Up a Buried Millipede? and Is My Millipede Dead or Moulting?.

In short, millipedes often bury themselves before moulting, but burying is also normal resting and hiding behaviour, so it should not be treated as proof of a moult.