Millipede lifespans vary a lot between species. Some of the smaller tropical species live two or three years. Large species like the giant African millipede can live seven to ten years with good care. That's a meaningful range, and it's worth knowing what you're signing up for before you buy one.
Lifespan by species
Archispirostreptus gigas (giant African millipede) is the one most people ask about, because it's the most commonly kept large species. In captivity, with good husbandry, they typically live 5-7 years, with some individuals reportedly reaching 10. Lifespan data for millipedes in captivity is imprecise because many keepers acquire animals of unknown age, so the clock starts from when the animal was purchased rather than when it was born. A wild-collected adult that's already several years old won't match the lifespan of a captive-bred juvenile raised from a pedeling.
Epibolus pulchripes (pink leg millipede) has a similar range, roughly 5-7 years, though reliable data for this species is sparser. Smaller species generally live shorter lives. Trigoniulus corallinus (rusty millipede) probably lives 2-4 years, though individual records are hard to come by since they're often kept in colonies where individual tracking is impractical.
North American species like Narceus americanus (the American giant millipede) are reported at 5-8 years in captivity. Some temperate species may live longer in cooler conditions, where their metabolic rate is lower and development is slower, but again, hard numbers are limited.
What affects lifespan?
Dehydration is the number one killer. If the substrate dries out, the millipede can't maintain its moisture balance and it goes downhill fast. Keep the substrate consistently damp and the humidity in the 70-85% range for tropical species. This single factor probably accounts for more premature deaths than everything else combined.
Calcium deficiency is slower but just as damaging over time. It causes failed moults and weak exoskeletons that accumulate problems. A millipede that's been calcium-deficient for months will have a shorter lifespan than one that's always had cuttlefish bone available.
Temperature plays a role too. Warmer conditions increase metabolic rate, which generally means faster growth but potentially a shorter overall lifespan. This is a common trade-off in ectotherms. Aim for the middle of the species' preferred range rather than pushing the upper limit constantly.
Substrate quality matters because the substrate is both home and food. If it's depleted, contains toxic softwoods, or has been contaminated with pesticides, the millipede's health suffers. Top it up with fresh rotting hardwood and leaf litter regularly. And finally, chronic stress from frequent disturbance, too much handling, or overcrowding takes a toll. Stressed animals don't live as long, even if the stress is hard to measure in an invertebrate.
Growth rate and maturity
Large millipede species grow slowly. A. gigas takes 3-5 years to reach full adult size from hatching. That means a significant proportion of their total lifespan is spent growing. They continue to moult as adults, though less frequently, and each moult carries a small risk of failure.
Smaller species reach maturity faster. T. corallinus can be mature within a year. This faster life cycle also correlates with their shorter overall lifespan.
How to tell if a millipede is old
There's no reliable way to age a millipede by looking at it, beyond distinguishing juveniles from adults by size and segment count. Old millipedes may become less active, feed less, and spend more time buried in the substrate. They may moult less frequently. But these can also be signs of illness or poor conditions, so don't assume a sluggish millipede is just old without checking your husbandry first.
When a millipede reaches the end of its natural lifespan, it typically becomes progressively less active, stops feeding, and eventually dies. There's no dramatic decline. They just gradually slow down.
Compared to other invertebrate pets
For context, millipedes are middling in terms of invertebrate lifespan. Jumping spiders live 1-3 years. Adult flower beetles live a few months (though the larval stage can add a year or more). Isopod colonies persist indefinitely even though individual animals live 2-5 years. Tarantulas are the long-lived outliers, with some female specimens exceeding 20 years.
A large millipede is a longer commitment than most invertebrate pets. Seven or more years with an A. gigas is comparable to a hamster or a gerbil. It's not a massive time commitment, but it's enough that you should be prepared for it rather than treating the animal as disposable.
Buying from known sources
If lifespan matters to you, which it should, try to buy captive-bred millipedes from breeders who can tell you the animal's approximate age. A wild-collected adult might already be several years old, and you'll have no way of knowing how much of its lifespan remains. A captive-bred juvenile, while smaller and less impressive to start with, gives you the full lifespan to enjoy and the satisfaction of watching it grow to adult size over the years.