Snake millipedes (order Julida) aren’t the flashiest millipedes. They sometimes make their way into homes and can derail trains, habits that people don’t generally view gracefully. We all have our flaws.
Sooner or later, you’re likely to run into one. The order is mainly Holarctic, but it can now be expected most anywhere thanks to transport by humans. The Julidae and Blaniulidae are shining examples of success through human assistance, and you’re probably not far from a representative of one of those species right now.
Ophyiulus pilosus (Julidae), a species native to Europe but now found widely across continents, including North America.
That’s not to say that all Julidans are drab and mucking around where they shouldn’t be, however. We have a number of native families here in North America, including my personal favorite, the Parajulidae. Parajulid males are instantly recognizable by their enlarged, almost tusk-like first leg pair.
A male Parajulid in the tribe Uroblaniulini from North Carolina, showing off its enlarged first leg pair.
While the Parajulids are my favorite, hands-down the most beautiful Julida in North America live over in potato country: Idaho. Represented by only one described species, the Chelojulidae are breathtakingly gorgeous. They’re instantly recognizable by their dorsal and lateral crests, a unique character within the Julida and more reminiscent of the Cambalidea or Callipodida.
Chelojulus sculpturatus (Chelojulidae) mating. Photo by Casey Richart, CC-BY.
Here in Virginia, I’m content with my Parajulids (while I plan my Idaho collecting trip). Another family I tend to find is the Blaniulidae, which are mainly found underneath and within logs. These are pale white to light brown millipedes which are very thin (we’re talking less than a millimeter in width), and not particularly interesting. Most of our species are introduced, except for Virgoiulus minutus, and males are very rare. Many Blaniulids reproduce via parthenogenesis, in which unmated females can lay viable eggs—no male necessary. It’s hypothesized that this parthenogenetic condition is a result of these millipedes’ bark-dwelling lifestyle (Enghoff 1994), a connection that has been documented within a number of Julidan families.
Proteroiulus fuscus (Blaniulidae), an introduced species from Europe. Species in this family often have a single line of ocelli, or they’re absent entirely.
I don’t have a ton of Blaniulids in my collection, partly because I focus on leaf litter when I’m out collecting instead of checking logs. It’s not a family I seek out since most species I’ll find are introduced, but I grab them when I happen across them. I take a quick look under the scope and identify them (or leave them at the family level if I’m pressed for time) and move on—maybe I’ll upload a photo to iNaturalist. That’s what I did last spring with a couple specimens I identified as Proteroiulus fuscus, and thought nothing more of them.
The aforementioned millipedes; note the triangular patch of ocelli.
But then a few weeks ago, my colleague Pierre-Marc Brousseau noted that the eye pattern didn’t match for P. fuscus, and he was right! Within the Blaniulidae, species have either one row of ocelli or lack ocelli—none have a triangular patch of ocelli like these ones. That left me with two options: either the Okeanobatidae or the Nemasomatidae, both of which are considerably rarer than the Blaniulidae.
The Nemasomatidae are unique within the Julida in having secondarily free sternites which aren’t fused to the pleurotergites, as in the other families of the order. I did a quick dissection of one of my specimens, and its sternites were fused to the pleurotergites (though the plate itself had slight sutures delimiting the edges of the sternites, which is typical but can be confusing if you haven’t seen Nemasomatid-type sternites before)—a match for Okeanobatidae.
In North America, we only have one species of Okeanobatidae, Okeanobates americanus, and this was it!
Two juveniles, Okeanobates americanus. Note the scale at the top: the black marks are millimeters. These are diminutive millipedes, with adults reaching a centimeter in length.
This was my first time seeing this species (and genus! and family!), a thrill! Its range in North America is limited to the Central Appalachian Mountains (North Carolina, Tennessee, Kentucky, and Virginia) north to Ontario and Quebec. After checking these two specimens, I went through all my specimens identified as Blaniulidae to search for other misidentifications, and I found three additional specimens. Two were from Montgomery County, Virginia, and one was from Monroe County, West Virginia. These specimens represent the second Virginia record for the species and the first record of the species for West Virginia. I bet they’re more widespread, but easily confused for other species, in addition to being tightly locked to their subcortical habitat and unlikely to be found outside of it. Obviously, I need to be checking logs more often.
O. americanus is very likely parthenogenetic (see discussion in Enghoff 1979), and the male has yet to be found. Even within parthenogenetic species, males pop up from time to time, though it’s quite rare. In their study of Virgoiulus minutus (Blaniulidae), Enghoff & Shelley (1979) examined about 875 specimens and found 4 males, coming out to about 0.5% of their specimens. If that ratio holds true for O. americanus, then we’ll still be searching for a while until we find a male.
Other species in the Okeanobatidae are known from Japan, representing a trans-Beringian connection between the myriapod fauna of East Asia and North America. This biogeographical connection has been recognized in a few other millipede families, such as the Nemasomatidae, Parajulidae, Andrognathidae, and Xystodesmidae.
While I was working on identifying these Okeanobates americanus, I realized that I would love to have a handy key to identify any Julida I collect in North America. Most of them I can pretty easily identify by sight, but uncommon families like the Blaniulidae and Nemasomatidae always send me searching through my computer for various references. To fix this, I wrote a key covering all families of Julida that occur in North America, native or introduced, presented below.
Many helpful characters were gleaned from the key in Enghoff (1991), which was written for use with adult males (and includes all Julidan families, rather than just ones occurring in North America). I’ve striven to make my key usable with adults of any sex, but I still include useful sexually dimorphic characters when available. I appreciate any feedback on the key, especially if you find errors.
Key to North American families of the millipede order Julida
last updated 27 Nov 2023
1a. Body rings with a pair of rounded crests dorsally and linear crests laterally……Chelojulidae.
Only known from northern Idaho, one species: Chelojulus sculpturatus. An exceptionally beautiful millipede.
Fig. 3 from Enghoff 1982, showing crests in dorsal view of Chelojulus sculpturatus
1b. Body rings lacking crests, at most with impressed striations………………………………...2.
2a. Epiproct bifurcate into two spines………………………………………Telsonemasomatidae.
6-12 mm long, 1-3 ocelli on each side of the head. One species, from Benton Co., Oregon.
Fig. 5 from Enghoff 1979, showing bifurcate epiproct of Telsonemasoma microps, colors inverted for clarity.
2b. Epiproct not produced, or if produced, not bifurcate……………………………….………....3.
3a. Body rings with strongly impressed striations encircling entire ring……………………………4.
3b. Body rings with slightly impressed striations only present below the level of the ozopores………. ...………………………………………………………………………………………………….6.
4a. Gnathochilarium with promentum short, only separating lamellae linguales basally; male first leg pair hook-like; body length ca. 7-30 mm..........……………………………………….…….Julidae.
An introduced family native to the Palearctic, common near human development. Often found in large numbers, occurs throughout North America.
4b. Gnathochilarium with promentum long, completely separating lamellae linguales; male first leg pair very short, with small tibial outgrowths directed sublaterad; body length ca. 16-165 mm………
………………………………………………………………..………..……Paeromopodoidea, 5.
5a. Large-bodied millipedes ca. 51-165 mm long, with broad longitudinal yellow stripes or dark to light transverse bands on body rings…………………...…………………………Paeromopodidae.
Western North America: distributed in California, Oregon, Washington, Idaho, and Montana; two genera: Paeromopus and Californiulus. Includes the largest millipedes in the Nearctic region.
5b. Small-bodied millipedes ca. 16 mm long, with body rings dark mottled brown and lacking longitudinal stripes or transverse bands…………………...……...…………Aprosphylosomatidae.
One species, Aprosphylosoma darcenae, only known from one locality in Josephine County, Oregon.
6a. Large-bodied millipedes ca. 19-58 mm long, diameter ca. 2 mm or more; strongly pigmented, light orange to dark purple; males with greatly enlarged first leg pair; ocelli present in a triangular field; mandibles with 6 or more pectinate lamellae………………………………..……Parajulidae.
Speciose and common throughout North America.
6b. Small-bodied millipedes ca. 5-20 mm long, diameter less than 1 mm; depigmented to bronze brown in color; male first leg pair not greatly enlarged, but may be modified into hook-like structures or have reduced podomeres; ocelli absent or present in a linear row or triangular field; mandibles with 4 or 5 pectinate lamellae……………………………..……………………………7.
7a. Sternites free from pleurotergites, with anterolateral wing-like expansions; eyes present in a triangular field; male first legs reduced in size, but not hook-like……….…...…….Nemasomatidae.
Two genera: Orinisobates and Thalasissobates. Orinisobates is associated with rotting logs in the Pacific Northwest and Central Appalachians, with disjunct records from Illinois, Florida, Utah, and Wyoming. Thalasissobates is associated with littoral habitats on the Atlantic Coast and has been reported from New Brunswick, Massachusetts, and Virginia.
Fig. 2 from Enghoff, 1985, showing the free sterna and the anterolateral wing-like expansions of Nemasoma varicorne.
7b. Sternites fused to pleurotergites, lacking anterolateral wing-like expansions; eyes absent or present in a linear series or triangular field; male first leg pair unmodified, slightly reduced in size, or modified into hook-like structures……………………..…………..………………Blaniuloidea, 8.
8a. Gnathochilarium with base of promentum straight or convex; ocelli absent or in a linear series; male mandibular cardo and stipes typically produced into a forceps-like structure.…….Blaniulidae.
Most species introduced from Europe, now found across the continent; one species (Virgoiulus minutus) native to eastern North America.
8b. Gnathochilarium with base of promentum concave; ocelli absent or in a triangular field; male mandibular cardo and stipes unmodified………………………………………...……………......9.
Modified Fig. 5 from Enghoff 1979, showing gnathochilarium of Okeanobates americanus. p: promentum
9a. Ocelli in a triangular field; mottled brown in color; gnathochilarium with laminae linguales not extending past base of promentum; female vulvae within a deep vulval invagination………………... …………………………………………………………………………………….Okeanobatidae.
One species, Okeanobates americanus, found from Ontario and Quebec south to North Carolina and Tennessee.
9b. Ocelli absent; pale, depigmented; gnathochilarium with laminae linguales extending past base of promentum and fitting into shallow concavities of the stipites; female vulvae within a short vulval invagination……………………………………………………………….…...…..Zosteractinidae.
Small cave-adapted millipedes, two genera. Ameractis is known from caves in Tennessee, Alabama, North Carolina, and Virginia. Zosteractis is reported from caves along the Mississippi River in Missouri and Illinois.
Modified Fig. 18 from Hoffman 1963, showing gnathochilarium of Ameractis satis.
References:
Blower JG (1985) Millipedes. Synopses of the British Fauna (New Series) 35. E. J. Brill, London, 242 pp.
Enghoff H, Shelley RM (1979) A revision of the millipede genus Nopoiulus (Diplopoda, Julida: Blaniulidae). Entomologica Scandinavica 10: 65–72.
Enghoff H (1979) A new genus and species of the millipede family Nemasomatidae (Diplopoda, Julida). Steenstrupia 5: 149–159.
Enghoff H (1979) The millipede genus Okeanobates (Diplopoda, Julida: Nemasomatidae). Steenstrupia 5: 161–178.
Enghoff H (1982) An extraordinary new genus of the millipede family Nemasomatidae (Diplopoda: Julida). Myriapodologica 1: 69–80. https://www.vmnh.net/content/vmnh/uploads/PDFs/research_and_collections/myriapodologica/myriapodologica_v1_n11.pdf
Enghoff H (1985) The milliped family Nemasomatidae. With description of a new genus, and a revision of Orinisobates (Diplopoda: Julida). Entomologica Scandinavica 16: 27–67.
Enghoff H (1991) A revised cladistic analysis and classification of the millipede order Julida with establishment of four new families and description of a new nemasomatoid genus from Japan. Zeitschrift fuer zoologische Systematik und Evolutionsforschung 29: 241–263.
Enghoff H (1994) Geographical parthenogenesis in millipedes (Diplopoda). Biogeographica 70: 25–31. https://www.researchgate.net/publication/289831304_Geographical_parthenogenesis_in_millipedes_Diplopoda
Hoffman RL (1961) A new genus and subfamily of the diplopod family Nemasomatidae from the Pacific Northwest. Proceedings of the Entomological Society of Washington 63: 58–64. https://www.biodiversitylibrary.org/page/16338831
Hoffman RL (1963) Taxonomic notes on some American Nemasomatid Diplopoda. Transactions of the American Entomological Society 89: 165–182. https://www.jstor.org/stable/25077858
Shelley RM (1994) Revision of the milliped family Paeromopodidae, and elevation of the Aprosphylosomatinae to family status (Julida: Paeromopodoidea). Entomologica Scandinavica 25: 169–214.