Semionellus placidus
This record describes Semionellus placidus (species). Recorded family: Xystodesmidae. Recorded order: Polydesmida.
Identification and Appearance
Paranota reduced, peach-colored and connected by a caudal peach metatergal band. Prozonite and anterior metazonite brown. Legs, antennae white. Gonopods: prefemoral process expanded into a corkscrew-like shape, acropodite whip-like. Females can be identified by the hairy receptacles of their cyphopods, which are smooth in other eastern Xystodesmid tribes. The only representative of the tribe Chonaphini in the eastern United States.
Classification
- Kingdom
- Animalia
- Phylum
- Arthropoda
- Class
- Diplopoda
- Order
- Polydesmida (Flat-backed Millipedes)
- Family
- Xystodesmidae
- Tribe
- Chonaphini
- Genus
- Semionellus
Imported taxonomy record. Source availability varies; see the source references and editorial policy below.
Habitat and Range
Habitat
In moist leaf litter of deciduous forests and cove habitats, usually near water.
Geographic Range
Sporadic occurs throughout its range: southeastern Minnesota and southern Wisconsin; central Indiana; central to southern Michigan and northwestern Ohio; southeastern Ohio; eastern West Virginia and western Virginia.
Seasonal Activity
Spring through fall
Diet and Behavior
Diet: Decaying leaves
Additional species information
Species notes from the sources
Etymology: Semionellus placidus (Wood, 1864)
About Flat-backed Millipedes: the wider group
Order-level background for Polydesmida, the group containing Semionellus placidus. Species-specific details appear above.
Group overview
Polydesmida (flat-backed millipedes) is the largest millipede order with ~3,500 described species. Many species produce hydrogen cyanide (HCN) as a chemical defense - a strategy unique among arthropods.
Ecological role of the group
Flat-backed millipedes are major leaf litter decomposers in forest ecosystems, recycling calcium, nitrogen, and other nutrients. Their fecal pellets contribute significantly to soil formation and humus production.
Economic and practical significance of the group
Millipedes are generally beneficial decomposers but can occasionally damage seedlings and soft fruits in gardens. Some tropical species cause skin irritation through their cyanide-based defensive secretions.
Recorded sources for this group: Myriapod research, soil ecology. Imported estimates may describe particular regions or reporting periods.
Photos of Semionellus placidus (5)
Photo credits: Contributed by v belov; Additional contributions by DerekHennen
Frequently Asked Questions About Semionellus placidus
What is Semionellus placidus?
Semionellus placidus is a species in the family Xystodesmidae, within the order Polydesmida.
How big is Semionellus placidus?
28 mm
How do you identify Semionellus placidus?
Paranota reduced, peach-colored and connected by a caudal peach metatergal band. Prozonite and anterior metazonite brown. Legs, antennae white. Gonopods: prefemoral process expanded into a corkscrew-like shape, acropodite whip-like. Females can be identified by the hairy receptacles of their cyphopods, which are smooth in other eastern Xystodesmid tribes.
Where is Semionellus placidus found?
| Feature | Details |
|---|---|
| Habitat | In moist leaf litter of deciduous forests and cove habitats, usually near water. |
| Range | Sporadic occurs throughout its |
| Range | southeastern Minnesota and southern Wisconsin; central Indiana; central to southern Michigan and northwestern Ohio; southeastern Ohio; eastern West Virginia and western Virginia. |
What does Semionellus placidus eat?
The diet of the Semionellus placidus includes Decaying leaves.
When is Semionellus placidus active?
Semionellus placidus: seasonal activity - Spring through fall.