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What humans know about the rolling, bulldozing Pill Millipedes (Glomeris marginata)!

Glomeris marginata
Photo: Botaurus stellaris (WikiCommons)

We are a very common species in the UK, a part of a big family of millipedes called Glomeridae, however, our order Diplopoda (commonly known as millipedes) is an understudied group of invertebrates. I am one of 62 species recorded in the UK in the last 40 years.

How to identify us in the Field:

In the UK we are a very distinctive species and unlikely to be confused with any other millipede inculding our closest UK relative (Geoglomeris jurassica, which is white and is less than a cm long!). Sometimes we can be mistaken for a pill woodlouse, which tend to be grey in colour.

Our most famous trait is the ability to roll into an egg shape, to create the perfect egg shape our last segment divides into three parts, this also helps to stop predators being able to unroll us.

Glomeris marginata rolled up
Photo: Keith Lugg (BMIG)

Life Cycle:

We have an interesting life cycle, we hatch around eight to ten weeks after our eggs have been laid, we are blind, and we start off with only three pairs of legs! As we grow we add on segments which have two pairs of legs, adding four legs to each segment. We can live up to ten or eleven years, reaching sexual maturity at around 3 years old.By then we have moulted around nine times and have approximately 18 pairs of legs and are about 2cm long on average! As adults, we still moult.

Our role within our habitats:

My humble fellow Pill Millipedes are detritivore and are mainly active at night. This is what makes millipedes overall so important to any environment they live in. Pill Millipedes digest decomposing plant matter helping to break it down into smaller pieces which aids the microorganisms in the soil and decomposing matter to break-down the leaves and other organic matter, which will eventually become soil. One study in France estimated that between 8% – 11% of the leaf litter in an oak woodland was consumed by the pill millipedes each year.

Where you can find us:

We are not just found in woodlands, you can find us for example in your back gardens if you have deciduous trees, like oaks, ash, beech and sycamore and lots of rotting vegetation. We are also found hanging out in places like mountains or cliffs, with a lot of bare rock, but we cannot live in areas which are very sandy or are disturbed by humans a lot, such as farmland. We also don’t like and are not commonly found in graveyards!

Glomeris marginata in wood Photo: Keith Lugg (BMIG)

Here are some general facts about our millipede family: 

Did you know worldwide there are over 12,000 species described as millipedes, though it is predicted that there may be up to 20,000 species worldwide. There are still a lot of species to identify and describe. Our prehistoric ancestors who lived in Scotland (genus –  Arthropleura) over 400 million years ago grew to around 2 meters long, today however the longest millipede is only around 40cms, the Giant African Millipede (Archispirostreptus gigas) with around 250 legs. But the millipede with the most legs is a millipede just a little bigger than me at around 3-4cm with over 600 legs called Illame plenipes!

If you have any question please send us a message.

If you are interested in learning more about millipedes, there is a UK society called the British Myriapod and Isopod Group which also cover centipedes and woodlice, which has lots of information about about millipedes.

Thank you for reading about us and please vote for the humble pill millipede!