Myriapoda

Distinguished from other arthropods by the combination of: terrestrial habitat, single pair of antennae, numerous leg-bearing segments, and tracheal respiration. Millipedes (Diplopoda) have two pairs of legs per apparent body segment (except first four segments), resulting from fusion of segment pairs; centipedes (Chilopoda), pauropods, and symphylans have one pair per segment. Centipedes possess venomous forcipules (modified first legs) beneath the head. Pauropods are minute (0.5–2.0 mm), soil-dwelling, with dorsal tergites fused across segment pairs. Symphylans have 6–12 leg pairs and resemble small centipedes superficially. Myriapods lack the three distinct body tagmata (head, thorax, abdomen) of insects.

Elongated, multi-segmented bodies with one pair of antennae. Leg count varies dramatically: from fewer than 10 legs in some minute species to over 1,300 in the millipede Eumillipes persephone. Body segments range from 15 to 173. Most possess simple eyes (ocelli), though several groups are eyeless: Symphyla, Pauropoda, millipede order Polydesmida, and centipede order Geophilomorpha. House centipedes (Scutigera) possess large compound eyes. Respiration occurs via spiracles connected to a tracheal system. A long tubular heart extends through much of the body with few associated blood vessels. Malpighian tubules handle nitrogenous excretion. The brain is relatively simple compared to other arthropods, with a syncerebrum composed of protocerebrum, deutocerebrum, and tritocerebrum.

Predominantly moist terrestrial environments: forests, leaf litter, soil, and rotting wood. Most abundant in tropical and temperate moist forests where humidity supports respiratory function through spiracles. Some species occupy grasslands, semi-arid habitats, and deserts. A very small percentage are littoral (seashore-dwelling). Pauropoda and Symphyla are strictly soil-dwelling in cryptic microhabitats. Some centipedes (e.g., Scutigera coleoptrata) are synanthropic, restricted to human dwellings. Extinct Arthropleura inhabited Carboniferous coal swamp forests. The Movile Cave in Romania hosts a unique troglobiont centipede (Cryptops speleorex) in a chemosynthetic, sulphur-rich ecosystem isolated for millions of years.

Worldwide distribution across all continents except Antarctica. Chilopoda and Diplopoda are globally distributed and species-rich. Pauropoda occur on all continents except Antarctica. Symphyla are cosmopolitan but poorly documented. Regional diversity hotspots include tropical rainforests of Borneo, Madagascar, and Southeast Asia. In Canada, 145 species are documented across four classes (54 Chilopoda, 66 Diplopoda, 23 Pauropoda, 2 Symphyla), with an estimated 93 additional species undiscovered. Chile hosts 75 millipede species with high endemism and seven introduced species. Cretaceous Burmese amber (ca. 100 mya) preserves 450+ millipedes representing 13 of 16 modern orders, indicating ancient lineage diversification.

Class-dependent. Chilopoda (centipedes): chiefly nocturnal predators consuming arthropods, earthworms, and small vertebrates including lizards and small rodents. Large tropical species (Scolopendra) capture snakes and small mammals. Diplopoda (millipedes): detritivores consuming decaying plant material, leaf litter, mosses, algae, fallen trees; some consume living or dead animal tissue. Pauropoda: soil detritivores. Symphyla: primarily detritivores, though some feed on fine roots and root hairs, with potential to damage crops.

Development is either epimorphic (all segments formed embryonically; Scolopendromorpha and Geophilomorpha) or anamorphic (segments added post-embryonically through successive molts). In anamorphic development, hatchlings emerge with few segments and legs (as few as three pairs), adding segments through molting until reaching adult form. Three types of anamorphosis are recognized: euanamorphosis (segments added throughout life, even after sexual maturity), emianamorphosis (segment addition ceases at a fixed stage, with further molts), and teloanamorphosis (segment addition stops at adult form, followed by no molting). Males produce spermatophores transferred externally to females through often complex mating behaviors. Females lay eggs in batches; symphylan eggs are white, spherical, with hexagonal ridges, hatching in up to 40 days. Lifespans range from 2–7 years in many millipedes, with potential for hundreds of offspring.

Centipedes are fast-moving, nocturnal hunters that detect prey through substrate vibrations, seizing victims with legs and injecting venom via forcipules. Some centipedes secrete sticky fluids to immobilize prey. Millipedes are slow-moving; many species curl into defensive balls (pill millipedes, Sphaerotheriida) or secrete noxious chemical defenses (benzoquinones, hydrogen cyanide, benzaldehyde) from segmental glands when disturbed. Several millipede and centipede species are bioluminescent. Symphylans and pauropods exhibit cryptic soil-dwelling behavior. House centipedes (Scutigera) are agile climbers active in human dwellings.

Critical decomposers in terrestrial ecosystems. Millipedes, pauropods, and symphylans fragment and consume decaying plant material, accelerating nutrient cycling in soil and leaf litter. Centipedes function as apex predators in soil and ground-dwelling arthropod communities, regulating populations of insects, worms, and other invertebrates. Myriapods serve as prey for vertebrates and larger invertebrates. Their burrowing activities contribute to soil aeration and structure.

Generally beneficial: centipedes control pest insects in gardens and homes; millipedes contribute to soil health through decomposition. Some millipede secretions can cause temporary skin blistering and discoloration; handling requires caution and hand washing. Large centipede bites (e.g., Scolopendra) cause intense pain and discomfort; fatalities are extremely rare. Symphylans can damage crop roots. Myriapods are subjects of scientific research (myriapodology), with dedicated societies and journals (International Journal of Myriapodology). Popular in museum education and pet trades. The extinct giant Arthropleura represents one of the largest terrestrial arthropods known.

• Hexapoda (insects)Insects have three body tagmata (head, thorax, abdomen) with three pairs of legs on thorax only; myriapods have numerous similar segments with legs throughout most of the body and lack the distinct thorax-abdomen division.
• CrustaceaCrustaceans are primarily aquatic, typically possess biramous appendages and gills; myriapods are obligate terrestrial with uniramous legs and tracheal respiration.
• ArachnidaArachnids have two body regions (cephalothorax and abdomen) with four pairs of legs; myriapods have many segments with numerous leg pairs and a single pair of antennae (arachnids lack antennae).

• terrestrial
• soil-dwelling
• detritivore
• predator
• venomous
• fossil
• tracheal respiration
• anamorphosis
• decomposer
• cryptic
• troglobiont
• bioluminescent

• BugGuide
• Wikipedia
• iNaturalist taxon
• NCBI Taxonomy
• Catalogue of Life
• Bohart Museum Open House: Many Legs, Many Eyes, Many Ears, Many Hands | Bug Squad
• Recyclers of the rainforest: Bornean myriapods, millipedes (Diplopoda), and their nemesis, giant centipedes (Chilipoda) — Bug of the Week
• Latest results of myriapod research from the 18th International Congress of Myriapodology | Blog
• Life and death down under - Garden millipedes (Order Julida) and stone centipedes (Genus Lithobius — Bug of the Week
• 450+ millipedes found in Cretaceous amber | Blog
• King of the Cave: New centipede on top of the food chain in the sulphurous-soaked Movile | Blog
• Myriapoda
• Myriapoda of Canada
• Catálogo de los milpiés (Myriapoda: Diplopoda) de Chile