Polydesmus angustus, also known as the flat-backed millipede, is a millipede

Millipede

Millipedes are arthropods that have two pairs of legs per segment . Each segment that has two pairs of legs is a result of two single segments fused together as one...

 in the genus Polydesmus.

Physical characteristics

Flat-backed millipedes resemble centipede

Centipede

Centipedes are arthropods belonging to the class Chilopoda of the subphylum Myriapoda. They are elongated metameric animals with one pair of legs per body segment. Despite the name, centipedes can have a varying number of legs from under 20 to over 300. Centipedes have an odd number of pairs of...

s. The bodies of the adults are flat, dark brown, with about twenty segments. They measure 14–25 mm (0.551181102362205–0.984251968503937 in) in length and are about 0.4 mm (0.015748031496063 in) wide. The plate segments covering the back are ridged along their lengths. The antennae

Antenna (biology)

Antennae in biology have historically been paired appendages used for sensing in arthropods. More recently, the term has also been applied to cilium structures present in most cell types of eukaryotes....

 and legs

Arthropod leg

The arthropod leg is a form of jointed appendage of arthropods, usually used for walking. Many of the terms used for arthropod leg segments are of Latin origin, and may be confused with terms for bones: coxa , trochanter , femur, tibia, tarsus, ischium, metatarsus, carpus, dactylus ,...

 are longer than in most other millipedes.

Geographic range

This species is found in Northwest Europe and was accidentally introduced to the southeastern United States

Southeastern United States

The Southeastern United States, colloquially referred to as the Southeast, is the eastern portion of the Southern United States. It is one of the most populous regions in the United States of America....

 and Atlantic Canada

Atlantic Canada

Atlantic Canada is the region of Canada comprising the four provinces located on the Atlantic coast, excluding Quebec: the three Maritime provinces – New Brunswick, Prince Edward Island, and Nova Scotia – and Newfoundland and Labrador...

.

Habitat

Flat-backed millipedes live in compost

Compost

Compost is organic matter that has been decomposed and recycled as a fertilizer and soil amendment. Compost is a key ingredient in organic farming. At its most essential, the process of composting requires simply piling up waste outdoors and waiting for the materials to break down from anywhere...

 piles, under tree bark

Bark

Bark is the outermost layers of stems and roots of woody plants. Plants with bark include trees, woody vines and shrubs. Bark refers to all the tissues outside of the vascular cambium and is a nontechnical term. It overlays the wood and consists of the inner bark and the outer bark. The inner...

, inside cracks in stumps and logs, or in loose soil with lots of decaying bits of leaves.

Diet

Polydesmus angustus feeds on roots, dead leaves, and other bits of decayed plant materials, as well as strawberries

Strawberry

Fragaria is a genus of flowering plants in the rose family, Rosaceae, commonly known as strawberries for their edible fruits. Although it is commonly thought that strawberries get their name from straw being used as a mulch in cultivating the plants, the etymology of the word is uncertain. There...

and other fruits.

Behavior and reproduction

The ridged body of this millipede helps it to push its way through the soil.

Mating occurs from late spring through the summer and then again in late summer through mid-fall. Males usually mate only once. The females store the sperm from a single mating and produce several batches of eggs. Young millipedes hatching earlier in the year reach adulthood in one year, while those hatching later require two.