Centipedes vs. Millipedes

 

Flat-backed millipede in the family
Paradoxosomatinae

The sound of an “oh no!“ as my neighbor was looking at the new compost in my garden bed made me turn around. She had found a whole host of little long multi-legged varmints crawling around the edge of the compost within the bed.  She viewed them as pests that I needed to dispose of.  I wasn’t sure.

First identify.  When submitted to iNaturalist, there was a whole variety of opinions about exactly what these were. There was agreement that they were arthropods known as millipedes in the family Paradoxosomatinae, but no specific identification was made. 

Scientist have grouped centipedes and millipedes together for identification because of their many segmented bodies. There are more than 3,000 known centipedes and an estimated 8,000 species. There are upwards of 7,000 known and 80,000 estimated species of millipedes.  The inability to make a specific identification is understandable.

Centipedes and millipedes are quite different in their effect on a garden. Both are beneficial, but in different ways. They are not something you want to destroy.

In addition to their long segmented bodies, they are alike in a number of ways: 

• Both have poor or non-existent vision and rely on other senses, like the feel of vibrations.
• The longest species of each measure about six inches in length.
• Both prefer dark, moist environments such as under stones, leaf litter, logs, bark, or soil crevices.
• Both are primarily nocturnal, emerging from their hiding places at night to hunt and feed.  
• Both are beneficial in the garden environment.  

Despite their similarities, their differences are more notable.  The easiest way to identify whether you’re seeing a centipede or a millipede is the number of legs on each body segment. Centipedes have one pair per body segment while millipedes have two. The difference in benefits they provide to the garden are also clear. Centipedes are predators and help to reduce the insect population, while millipedes are decomposers and eat decaying plants and other organic matter, rarely attacking live plants.  

Feature	Centipede	Millipede
Legs	One pair per body segment, legs stick out from the sides	Two pairs per body segment, located underneath the body
Body Shape	Flattened	Rounded
Antennae	Long and whip-like	Short and elbowed
Movement	Fast	Slow
Diet	Carnivorous; preys on insects and other small arthropods	Detritivores; eats decaying plants and other organic matter
Defense	Venomous bite (not usually dangerous to humans)	Curl into a ball and may secrete irritating fluid
Lifespan	1-6 years	2-10+ years

This is once again a reminder to identify what you’re seeing before you destroy something that may be beneficial to your garden.

More info:  

https://carnegiemnh.org/centipede-or-millipede-whats-the-difference/

https://edis.ifas.ufl.edu/publication/IG093

https://content.ces.ncsu.edu/garden-millipede