25 Millipedes in California: Species, Habitats, and What Makes Each One Unique
August 23, 2026
California is home to a surprisingly diverse cast of millipedes—from introduced species thriving in backyard gardens to rare endemics found nowhere else on Earth. With more than 25 recognized species recorded across the state, California ranks among the most millipede-rich regions in North America, a fact that often surprises even seasoned naturalists.
These multi-legged decomposers play a quiet but critical role in California’s ecosystems. By breaking down leaf litter, rotting wood, and organic debris, millipedes help cycle nutrients back into the soil, supporting the plant communities that everything else depends on. Some species are so specialized that they exist within just a few square miles of a single California county.
This guide covers all 25 millipede species documented in California—their identifying features, preferred habitats, behaviors, and the ecological roles that make each one worth knowing. Whether a reader encounters one curling up under a garden pot or stumbles across a rare endemic on a forest hike, this resource offers the detail needed to identify and appreciate what they’ve found. For anyone already interested in millipede biology and behavior, California’s species diversity offers an exceptional case study.
Key Insight: California hosts both native millipede species found nowhere else on the planet and introduced species that have spread globally through the horticultural trade. Understanding which is which helps contextualize each species’ role in local ecosystems.
1. Common Millipede
The common millipede (Diploiulus luscus) is one of the most frequently encountered millipede species in California’s urban and suburban environments. Despite its name suggesting ordinariness, this species has a fascinating backstory as a European native that has successfully colonized much of the western United States through the movement of soil and plant material.
In California, D. luscus typically appears in gardens, compost heaps, and under mulch layers where moisture is consistently available. It has a slender, cylindrical body that ranges from pale gray to dark brown, usually reaching about 20–30 mm in length. The segments are clearly defined, and the animal moves with the characteristic smooth, wave-like leg motion shared by most julid millipedes.
This species is a dedicated detritivore, feeding almost exclusively on decaying plant matter. It poses no threat to healthy plants, though it may occasionally nibble on seedlings in very moist conditions. Gardeners who find them in large numbers after rain events can take comfort knowing these animals are doing valuable soil-conditioning work.
Pro Tip: If common millipedes are appearing frequently inside a home, the most effective long-term solution is reducing moisture around the foundation—fixing leaky gutters, improving drainage, and pulling mulch away from exterior walls.
2. Bulb Millipede
The bulb millipede (Nopoiulus minutus) earns its common name from its association with bulb crops and the damage it can occasionally cause to stored or planted bulbs. This species is another European introduction that has become well established in California, particularly in agricultural zones and intensively managed gardens throughout the Central Valley and coastal counties.
N. minutus is notably small—typically under 15 mm in length—with a pale, almost translucent body that can make it difficult to spot without close inspection. It favors cool, damp conditions and is most active during the wetter months of California’s Mediterranean climate, often retreating deeper into the soil during hot, dry summers.
While bulb millipedes are primarily decomposers, they have been documented feeding on the soft tissue of tulip, daffodil, and iris bulbs, particularly when those bulbs are already damaged or rotting. This opportunistic feeding behavior is what gives the species its somewhat unflattering reputation among horticulturalists. In natural settings away from cultivated plants, it performs the same beneficial decomposition role as most other millipede species.
3. Greenhouse Millipede
True to its name, the greenhouse millipede (Orthomorpha gracilis) has become a fixture in California’s commercial greenhouse operations and indoor plant nurseries. Originally from Southeast Asia, this species has spread globally through the international plant trade and is now considered cosmopolitan in distribution—found on every continent where greenhouse agriculture exists.
O. gracilis is a flat-backed millipede with a distinctly different body plan from the cylindrical julid species. Its body is somewhat flattened dorsally, with lateral keels (projecting flanges) along each segment, giving it a more angular appearance. Adults reach approximately 22–35 mm in length and display a dark brown to reddish-brown coloration with lighter leg coloration.
In California, this species thrives wherever potted plants, greenhouse benches, and moist growing media create a stable humid microhabitat. It feeds on decomposing organic matter in potting soil and rarely damages healthy roots, though it can become a nuisance in high densities. Growers who notice large populations should check for overwatering, as excess moisture is the primary driver of greenhouse millipede population explosions.
Important Note: Like many polydesmid millipedes, Orthomorpha gracilis can produce hydrogen cyanide as a defensive secretion when threatened. While the quantities are far too small to harm humans, handling should be done carefully and hands washed thoroughly afterward.
4. Yellow-Spotted Millipede
The yellow-spotted millipede (Harpaphe haydeniana) is one of California’s most visually striking native species and one of the easiest to identify in the field. Its jet-black body is lined with bright yellow spots along the lateral margins of each segment—a classic example of aposematic coloration, where bold patterns advertise the presence of chemical defenses to potential predators.
This species is native to the Pacific Coast of North America and is commonly found in the moist coniferous and mixed forests of Northern California, the Sierra Nevada foothills, and the Coast Ranges. It favors areas with abundant Douglas fir and redwood leaf litter, where it serves as a primary decomposer of the tough, slow-to-break-down needles and bark that accumulate on the forest floor.
H. haydeniana produces hydrogen cyanide through a chemical reaction between two compounds stored in separate glands—a defense mechanism that makes it unpalatable to most predators. Despite this, some birds and invertebrates have developed tolerance for the compound. The species is also a favorite subject in educational settings because its defensive chemistry is dramatic enough to be detected by smell (a faint almond scent) without posing real danger to careful human observers. Those interested in other fascinating California invertebrates might also enjoy exploring the diverse beetle species found across the state.
5. Long-Flange Millipede
The long-flange millipede (Trigoniulus corallinus) brings a splash of unexpected color to California’s millipede fauna. This small but vivid species displays a striking coral-red to orange-red body coloration that makes it immediately recognizable among the leaf litter and soil where it lives. Originally native to Southeast Asia and the Pacific Islands, it has established populations in California through the ornamental plant trade.
T. corallinus is a relatively small species, typically reaching 15–25 mm in length, with a smooth, cylindrical body and the characteristic red-orange pigmentation that has made it popular in the exotic pet trade. In California, established populations have been recorded in Southern California counties, particularly in areas with subtropical landscaping and year-round moisture.
This species is a strict detritivore and poses no threat to living plants or animals. Its small size and vivid coloration make it a frequent subject of curiosity for gardeners who encounter it unexpectedly. Because it is a non-native species, its ecological interactions with California’s native millipede fauna are still being studied, though it appears to occupy a similar decomposer niche without direct competition with most native species.
6. Paeromopus angusticeps
Among California’s native millipede fauna, Paeromopus angusticeps represents a genus with deep evolutionary roots in the western United States. This species belongs to the family Xystodesmidae, a group of flat-backed polydesmid millipedes that are particularly diverse in the mountainous regions of California and the broader Pacific Coast.
P. angusticeps is found primarily in the forested habitats of Northern and Central California, where it occupies the moist microhabitats beneath logs, rocks, and deep leaf litter. Like other xystodesmid millipedes, it has a distinctly flattened body with pronounced lateral keels, giving it a wider, more robust appearance than the cylindrical julid species. Body coloration tends toward dark brown to reddish-brown with subtle patterning along the dorsal surface.
This species is considered a native California endemic and plays an important role in the decomposition of woody debris on forest floors. Its relatively limited distribution makes it of interest to conservation biologists monitoring the health of California’s native invertebrate communities. Habitat disturbance, particularly logging and the conversion of native forest to other land uses, represents the primary threat to this and related Paeromopus species.
7. Paeromopus paniculus
A close relative of P. angusticeps, Paeromopus paniculus is another native California xystodesmid millipede with a distribution centered in the state’s forested mountain ranges. The two species share many ecological characteristics but differ in morphological details that require close examination to distinguish reliably in the field.
P. paniculus tends to favor slightly drier forest conditions than some of its congeners, occupying habitats in the mixed conifer forests of the Sierra Nevada and the inner Coast Ranges where seasonal moisture patterns create distinct wet and dry periods. During dry summer months, this species retreats into the deeper soil layers or beneath large, moisture-retaining logs where conditions remain humid enough for survival.
Research on Paeromopus species in California has been limited compared to more economically significant millipede groups, meaning much of the detailed ecology of P. paniculus remains to be documented. What is known suggests a typical polydesmid lifestyle centered on the decomposition of woody debris and leaf litter, with chemical defenses playing an important role in predator avoidance.
Key Insight: The genus Paeromopus is considered endemic to the western United States, making California’s populations of particular scientific and conservation significance. These species cannot be found anywhere else on Earth.
8. Illacme plenipes
No discussion of California’s millipedes would be complete without Illacme plenipes—the animal with the most legs of any creature on Earth. This extraordinary species holds the verified world record for leg count, with one specimen documented carrying 750 legs, though individuals typically have between 300 and 400. The species belongs to the ancient family Siphonorhinidae and represents a lineage with origins stretching back hundreds of millions of years.
I. plenipes is known only from a small area of San Benito County in Central California, making it one of the most geographically restricted millipede species in the world. It lives underground in sandstone rock formations, where it feeds on fungal material and decaying organic matter within the rock matrix. Its extreme leg count is thought to be an adaptation for moving through tight spaces in its subterranean habitat, where more legs mean more purchase against rock surfaces.
The species was first described in 1928 but went unrecorded for nearly 80 years before being rediscovered in 2005 by researchers from the University of Arizona. Subsequent studies have revealed remarkable anatomical features, including silk-producing hairs on its body that may help it adhere to rock surfaces. Scientific reporting on record-breaking legged animals frequently references this California species as a benchmark for myriapod diversity. Its extreme rarity and restricted range make it a priority species for California invertebrate conservation.
9. Illacme socal
Illacme socal is a more recently described relative of I. plenipes, discovered in Southern California and representing a significant range extension for this ancient millipede genus. While it does not match its famous cousin’s leg count, I. socal is still an exceptionally leg-rich species by any standard and shares many of the same morphological peculiarities that make the Illacme genus so scientifically fascinating.
This species was formally described in the 2010s following targeted surveys of Southern California’s serpentine and sandstone geological formations—the same types of substrate that host I. plenipes in the north. Its discovery confirmed that the Illacme lineage has a broader distribution within California than previously understood, though both species remain highly localized within their respective ranges.
Like I. plenipes, I. socal is a subterranean specialist with limited surface activity. This makes population surveys extremely challenging, and the full extent of its range and population size remains poorly understood. The discovery of this species underscores how much remains to be learned about California’s underground invertebrate fauna, even in a state that has been studied by naturalists for well over a century.
10. Brachycybe rosea
Brachycybe rosea is a member of the family Andrognathidae and one of California’s most charming native millipede species. Unlike the robust, armored appearance of many polydesmid millipedes, Brachycybe species have a slender, almost delicate body plan and are known for an extraordinary behavioral trait: parental care. Adult females of this genus guard their egg clutches and newly hatched young—a behavior that is exceptionally rare among millipedes.
This species is found in the moist forests of Northern California, where it lives beneath the bark of rotting logs and in the decaying wood itself. Its pale pink to rose-colored body gives it an immediately distinctive appearance that sets it apart from California’s darker-colored native species. Adults are relatively small, typically reaching 15–20 mm in length, with a narrow body and short legs adapted for life within the tight spaces of decaying wood.
B. rosea feeds on fungal mycelium growing within rotting wood rather than on the wood itself—a dietary specialization that places it in an important ecological position as a regulator of fungal communities within decomposing logs. This fungus-feeding habit is shared with its close relatives and represents a fascinating ecological niche within California’s forest floor communities.
11. Brachycybe producta
A close relative of B. rosea, Brachycybe producta shares the same general body plan and ecological preferences but differs in morphological details and has a somewhat different distribution within California. Both species are members of the same genus and display the remarkable egg-guarding behavior that makes Brachycybe millipedes so scientifically interesting.
B. producta is associated with the mature deciduous and mixed forests of California’s Coast Ranges and foothill zones, where sufficiently large and well-rotted logs provide the stable microhabitat this species requires. Because it depends on large-diameter coarse woody debris, its presence is often used as an indicator of old-growth forest characteristics—habitats that have become increasingly rare across California’s landscape.
The fungus-feeding lifestyle of B. producta means that it is intimately connected to the health of the wood-decay fungal community in its habitat. Changes in forest composition, moisture regimes, or the availability of large woody debris can all affect this species’ local abundance. Conservation of mature forest habitats in California is therefore directly relevant to the persistence of this and related Brachycybe species.
Pro Tip: To find Brachycybe millipedes in the field, look beneath the bark of well-rotted hardwood logs in moist forest settings. The pale pink coloration makes them easier to spot than many other millipede species once the bark is carefully lifted.
12. Xystocheir dissecta
Xystocheir dissecta is a California native belonging to the family Xystodesmidae—the same family as the Paeromopus species covered earlier. This species is found in the oak woodlands and chaparral-adjacent habitats of Central and Southern California, occupying a slightly drier ecological niche than many of its forest-dwelling xystodesmid relatives.
The body of X. dissecta is broad and flattened in the typical polydesmid fashion, with well-developed lateral keels on each segment. Coloration tends toward dark brown with subtle reddish tones, providing effective camouflage against the bark and leaf litter of its preferred habitat. Adults are medium-sized for a California millipede, reaching approximately 30–40 mm in length.
This species is most active during California’s wet season, when rainfall softens the soil and leaf litter becomes moist enough to support millipede foraging. During the long dry summer, X. dissecta aestivates in the deeper soil layers or within rotting wood, emerging again with the first autumn rains. This seasonal activity pattern is characteristic of many California native millipedes adapted to the Mediterranean climate’s pronounced wet-dry cycle.
13. Tylobolus deses
Tylobolus deses belongs to the family Spirobolidae and represents a different millipede lineage from the flat-backed polydesmids that dominate much of California’s native fauna. Spirobolid millipedes are large, cylindrical species with a more robust body plan, and T. deses is one of California’s more impressive native species in terms of sheer size.
This species is found in the chaparral, oak woodland, and coastal scrub habitats of Southern California, where it occupies the leaf litter and soil beneath shrubs and along creek margins. Its cylindrical body can reach 60–80 mm in length, making it one of the larger native millipedes in the state. Coloration is typically dark brown to reddish-brown, with a smooth, polished-looking dorsal surface.
T. deses is a dedicated decomposer of leaf litter and woody debris, and its large body size means it can process significant quantities of organic material. Like other spirobolid millipedes, it rolls into a tight coil when disturbed—a defensive behavior that protects its softer ventral surface and legs while presenting the harder, more protected dorsal surface to potential predators. California residents who enjoy observing the state’s diverse wildlife may find that lizard species in the same habitats are among the primary predators of this and similar millipede species.
14. Hiltonius pulchrus
Hiltonius pulchrus is a member of the family Polydesmida and one of three Hiltonius species found in California. The genus is endemic to the Pacific Coast of North America, making all three California Hiltonius species part of a lineage with deep regional evolutionary history. H. pulchrus is considered the most visually distinctive of the three, with coloration and body proportions that differ noticeably from its congeners.
This species is associated with the moist forest habitats of Northern California, particularly in areas with dense canopy cover and abundant leaf litter accumulation. It is most frequently found beneath logs and rocks in well-shaded forest understory environments, where the combination of moisture retention and organic material availability creates ideal conditions for a polydesmid millipede.
Like other polydesmid millipedes, H. pulchrus possesses ozopores—specialized glands along the sides of its body segments that produce defensive chemical secretions. These secretions serve as the primary defense against invertebrate and vertebrate predators and are responsible for the distinctive odor that many polydesmid millipedes produce when handled or disturbed.
15. Hiltonius hebes
Hiltonius hebes is the second of California’s three Hiltonius species and occupies a somewhat different geographic range within the state compared to H. pulchrus. While all three species share the same family and genus, they appear to have diverged in response to different habitat conditions across California’s varied landscape, resulting in distinct distributions that reflect the state’s extraordinary geographic and ecological diversity.
This species tends to be found in intermediate forest habitats—neither the wettest coastal forests nor the driest interior woodlands—where moisture availability is seasonal but reliable. Its body plan follows the standard polydesmid template: flattened, with lateral keels, and equipped with the chemical defense glands characteristic of the order. Coloration is typically in the brown to dark brown range with subtle variation across segments.
The ecology of H. hebes has not been studied as intensively as more economically prominent millipede species, but its role as a decomposer in California’s forest floor communities is well established. The presence of multiple Hiltonius species in California with overlapping but distinct ranges suggests a history of geographic isolation and speciation driven by the state’s complex topography.
16. Hiltonius australis
The third member of California’s Hiltonius trio, Hiltonius australis, has a distribution centered in the southern portion of the state—as its species name (meaning “southern”) suggests. This species occupies the transitional zone between California’s Mediterranean-climate forests and the more arid habitats of Southern California, giving it a slightly different ecological profile from its more northerly congeners.
H. australis is adapted to the more pronounced seasonality of Southern California’s climate, where the dry season is longer and more intense than in the northern parts of the state. This likely means the species has evolved behavioral or physiological strategies for surviving extended dry periods—either through deeper soil retreat, reduced metabolic activity, or both.
The discovery and formal description of all three Hiltonius species reflects the broader pattern of millipede diversity in California, where careful taxonomic work has repeatedly revealed that what appears to be a single widespread species is actually multiple distinct species with more restricted ranges. This pattern of cryptic diversity is common in soil invertebrates and suggests that California’s millipede fauna may be even richer than current records indicate.
Key Insight: The three Hiltonius species in California—H. pulchrus, H. hebes, and H. australis—represent a classic example of geographic speciation along a north-south gradient, driven by California’s dramatic climate variation from the Oregon border to the Mexican border.
17. Bdellozonium cerviculatum
Bdellozonium cerviculatum belongs to the family Bdellozonidae, a small and scientifically fascinating millipede family with a distinctly unusual body plan. Members of this family have an elongated, worm-like appearance that sets them apart from the more typical millipede silhouette, and B. cerviculatum is the primary California representative of this distinctive group.
This species is found in the humid forest habitats of Northern California, where it occupies the soil and decaying organic matter layer. Its elongated body, reduced lateral keels, and somewhat worm-like movement make it easy to overlook or misidentify in the field—observers unfamiliar with this family may not immediately recognize it as a millipede at all. Coloration is typically pale to medium brown, providing effective camouflage in the forest floor environment.
The ecology of B. cerviculatum is consistent with other forest-floor millipedes: it feeds on decomposing organic matter and contributes to nutrient cycling in the habitats where it occurs. Its unusual morphology may reflect adaptations to a more fossorial (burrowing) lifestyle than the typical surface-dwelling polydesmid, though detailed behavioral studies of this species in California are limited.
18. Stenozonium exile
Stenozonium exile is another member of the Bdellozonidae family, closely related to B. cerviculatum and sharing many of the same morphological characteristics that define this unusual millipede group. The genus Stenozonium is found primarily in the western United States, with California representing an important part of its range.
This species occupies similar habitat types to B. cerviculatum—moist forest floor environments in Northern and Central California where deep organic matter accumulation provides both food and shelter. Its slender, elongated body is well suited to navigating the dense matrix of decomposing leaves, fungal threads, and soil particles that make up its microhabitat.
S. exile is rarely encountered in large numbers and is considered uncommon across its range, though this may partly reflect the difficulty of detecting such a cryptic species rather than genuinely low population densities. Pitfall trapping and careful soil sifting in appropriate habitats have yielded most of the known California records for this species. Its presence is generally taken as an indicator of undisturbed, mature forest conditions.
19. Cylindroiulus caeruleocinctus
Returning to the cylindrical julid millipedes, Cylindroiulus caeruleocinctus is a European introduction that has become established in parts of California, particularly in the cooler, moister regions of the state where conditions approximate the temperate European habitats from which it originates. It is one of several Cylindroiulus species that have spread beyond their native range through human activity.
This species has a smooth, cylindrical body with the characteristic julid body plan: many segments, two pairs of legs per segment, and a rounded cross-section. Adults reach approximately 20–30 mm in length and display a grayish-brown to dark brown coloration with a subtle bluish iridescence in some lighting conditions—a feature reflected in the species name “caeruleocinctus” (meaning blue-banded).
In California, C. caeruleocinctus is most frequently found in urban parks, gardens, and landscaped areas where European plant species and soil amendments may have facilitated its establishment. It feeds on decomposing plant material and poses no threat to living vegetation. Its presence in California is a reminder of how thoroughly the global movement of plants and soil has reshuffled invertebrate communities worldwide. Those curious about other introduced invertebrates in California might also explore the snail species found across the state, many of which share a similar introduction history.
20. Cylindroiulus truncorum
A close relative of C. caeruleocinctus, Cylindroiulus truncorum is another European julid millipede that has established populations in California. The two species are morphologically similar and can be difficult to distinguish without microscopic examination of the gonopods (reproductive appendages used in millipede taxonomy), but they appear to have slightly different habitat preferences within the state.
C. truncorum tends to be associated with decaying wood and bark, making it more common in wooded areas and forest edges than in open garden settings. This preference for woody substrates distinguishes it somewhat from the more generalist C. caeruleocinctus and may explain why the two species can coexist in the same general area without direct competition for identical resources.
Like all julid millipedes, C. truncorum coils into a tight spiral when disturbed—a defensive posture that protects the legs and ventral surface while presenting the harder dorsal surface to potential threats. This behavior, combined with chemical secretions from glands along the body, provides effective protection against most invertebrate predators, though it offers less protection against vertebrate predators with greater persistence.
21. Ophyiulus pilosus
Ophyiulus pilosus is yet another European julid millipede that has made California its adopted home. This species is distinctive among the introduced julids for the fine hairs (setae) that cover its body segments—a feature reflected in the species name “pilosus” (meaning hairy). These setae give the animal a slightly fuzzy appearance under magnification that distinguishes it from the smooth-bodied Cylindroiulus species.
In California, O. pilosus has been recorded primarily in the coastal counties and the San Francisco Bay Area, where the mild, moist climate most closely resembles the temperate European conditions from which it originates. It is a common species in European gardens and has followed the same pathway as many other introduced millipedes—arriving in California through the movement of nursery stock and horticultural soil.
This species feeds on decomposing plant matter and fungi in the soil layer, contributing to nutrient cycling in the urban and suburban habitats where it is most common. Its relatively small size (typically 15–25 mm) and cryptic coloration mean it is often overlooked even by attentive gardeners, though it may be present in surprisingly high densities in suitable habitat patches. Anyone noticing unusual invertebrate activity in California gardens might also want to check for the ant species that often share the same soil microhabitats.
22. Opiona fisheri
Opiona fisheri is a California native millipede belonging to a genus with a distribution centered in the western United States. This species represents the kind of regionally endemic millipede that makes California’s invertebrate fauna so scientifically valuable—a species with no native range outside the state and a biology that reflects millions of years of adaptation to California’s specific environmental conditions.
This species is found in the oak woodland and chaparral habitats of Central California, where it occupies the leaf litter and soil beneath native shrubs and trees. Its morphology follows the general polydesmid pattern, with a flattened body, lateral keels, and chemical defense glands, but the specific features of its gonopods and body proportions distinguish it from other California polydesmids at the species level.
O. fisheri is named in honor of a naturalist who contributed to the documentation of California’s invertebrate fauna—a reminder that much of what is known about California’s millipede diversity is the result of dedicated field collection and taxonomic work by individual researchers over many decades. The species’ ecology is consistent with other native California polydesmids: a decomposer of leaf litter and woody debris, active primarily during the wet season, and aestivating during the dry summer months.
Common Mistake: Many people assume that all millipedes found in California gardens are introduced pest species. In reality, several native California millipede species also occur in garden settings, particularly in gardens that incorporate native plants and natural mulch layers. Proper identification matters for understanding ecological context.
23. Paeromopus angusticeps angusticeps
Paeromopus angusticeps angusticeps is the nominate subspecies of P. angusticeps—meaning it is the subspecies that was formally described first and carries the same name as the parent species. In millipede taxonomy, the recognition of subspecies reflects geographic variation within a species that is significant enough to document but not sufficient to warrant full species status.
This subspecies is associated with specific forest communities within the broader range of P. angusticeps in California, occupying habitat types where the combination of moisture, substrate, and forest composition creates conditions slightly different from those preferred by other subspecies or populations. The distinctions between subspecies in this group are primarily morphological and require specialist examination to confirm.
The recognition of subspecies within California’s native millipede fauna reflects the ongoing refinement of taxonomic understanding in this group. As molecular tools have become more widely applied to millipede systematics, it has become increasingly possible to detect genetic differentiation between populations that appear morphologically similar—work that is gradually reshaping understanding of how many distinct evolutionary lineages California’s millipede fauna actually contains.
24. Mitocybe auriportae
Mitocybe auriportae is a member of the family Julida and represents one of California’s less frequently documented millipede species. The genus Mitocybe has a distribution centered in the western United States, and M. auriportae is among the California representatives of this native julid lineage—distinct from the introduced European julids that have colonized the state’s urban environments.
This species is found in the natural habitats of California rather than in disturbed urban or agricultural settings, making it a useful indicator of relatively undisturbed native ecosystems. Its preferred habitat includes the leaf litter and soil of oak woodlands and mixed forests, where it feeds on decomposing organic matter in the typical julid fashion.
The species name “auriportae” (meaning “golden gate”) is a reference to the San Francisco Bay Area, reflecting the geographic associations of early collections of this species. Its presence in the Bay Area’s natural open spaces underscores the importance of preserving remnant native habitat patches within California’s most urbanized regions, where native invertebrate communities can persist if sufficient habitat quality is maintained. For those interested in other native wildlife sharing these habitats, California’s salamander species often occupy the same moist forest floor environments as native millipedes.
25. Ischnocybe plicata
Ischnocybe plicata rounds out the list of California’s documented millipede species and belongs to a genus with a characteristically western North American distribution. This species is a member of the family Julida and shares the cylindrical body plan of the other julid millipedes in this guide, though its native status distinguishes it from the introduced European julids that have become so widespread in California’s urban areas.
This species is associated with the natural forest and woodland habitats of Northern California, where it occupies the soil and leaf litter layer in a manner consistent with other native julid millipedes. Its relatively slender body and smooth segmentation give it a typical julid appearance, and distinguishing it from introduced julid species in the field requires attention to morphological details that are often only resolvable under magnification.
I. plicata contributes to the decomposition of organic matter in its native habitat and represents part of the native invertebrate community that existed in California long before the arrival of European species. Protecting the native forest habitats where this and other native julid millipedes persist is essential for maintaining California’s full complement of millipede diversity—a diversity that, as this guide demonstrates, extends far beyond the few introduced species most Californians are likely to encounter in their gardens.
California’s 25 documented millipede species tell a layered story about the state’s ecological history, geographic complexity, and the ongoing interplay between native wildlife and introduced species. From the record-breaking Illacme plenipes hidden in San Benito County’s sandstone to the common millipedes turning compost in Bay Area gardens, each species occupies a distinct place in California’s ecological web. Understanding and protecting this diversity—particularly the many native endemics with no populations outside the state—is a meaningful part of caring for California’s remarkable natural heritage. For readers eager to explore more of California’s invertebrate life, the state’s spider species, wasp diversity, and fly fauna offer equally fascinating windows into the world of California’s smaller residents.