Scientific name
Oniscus asellus
Oniscus asellus is a familiar woodlouse whose broad, relatively smooth adults differ greatly from juveniles. Identity must therefore not be based on a single colour or juvenile photograph. [1]
Origin
Very widespread in Great Britain and Ireland; also documented in damp German habitats. The BMIG profile used concerns the nominate subspecies asellus. [1][2]
- Flattened
- Humid shelters
- Distinctive young
Natural-history synthesis; no validated captive protocol in the selected sources.
At a glance
Adult Oniscus asellus are broad and relatively smooth; young animals have a different appearance, to be considered during identification. [1]
| ADULT SIZE | 11–18 mm Bodentier⁴; BMIG states up to 18 mm. [1][2] |
|---|---|
| LIFESPAN | Not established No supported individual lifespan in the selected sources. |
| LIFESTYLE | Ground-dwelling Under wood, stones and litter; escapes when disturbed. [1][2] |
Adult size
11–18 mm according to Bodentier⁴; BMIG states up to 18 mm for adults of the nominate form. [1][2]
Lifespan
Individual lifespan not established in the selected sources.
Lifestyle
Stays close to the ground beneath wood, stones and litter; may first become motionless, then move rapidly if disturbed. [1][2]
Housing
NATURAL ENVIRONMENT
Humid ground-level shelters — Documented natural context; no enclosure volume validated by these sources. [1][2]
No captive dimensions validated in these sources. Humid shelters in contact with the ground form the natural context to understand, not an enclosure protocol to copy. [1][2]
Care parameters
CAPTIVE CLIMATE
Not established — No validated husbandry range in the selected sources.
Humidity
Damp natural environment — Damp wood and litter; no home-husbandry percentage inferred. [1][2]
Humidity
Association with humid microhabitats [1][2] Record wood and litter condition; no universal relative humidity is inferred.
Temperature
Not quantified in the selected profiles Presence in a temperate region does not define a heating instruction.
Feeding
DIET AND CALCIUM
No species-specific daily ration or calcium dose is established by the profiles consulted. Occurrence locations do not constitute a menu. [1][2]
Scope of this profile
Natural-history synthesis; no validated captive protocol in the selected sources.
Identifying adults and young
The continuous body outline, three segments of the antennal flagellum and absence of the visible lung patches found in some other genera are useful characters. Juveniles may show tubercles and orange patterns, unlike the smoother appearance of large individuals. [1] Photographing several stages avoids artificially creating two species in one record.
One species, several contexts
BMIG also notes an occidentalis subspecies and intermediate forms in some British populations. [1] This profile retains a single species entry and does not presume the subspecies of a garden animal. To make data usable, record location, date and visible characters; geographical precision does not replace morphological examination.
Shelter, substrate and air
Bodentier⁴ finds the species particularly beneath decaying wood in deciduous forests and in garden organic matter. [2] This describes contact with complex shelters. An artificial enclosure is not equivalent to a forest stump: its drying, ventilation and material renewal would require their own documentation. No minimum height or depth is therefore added here.
Diet and calcium: keeping questions open
The profiles consulted set no daily ration or calcium dose for O. asellus. An encounter in compost does not authorise treating every composting material as suitable food. In monitoring already under way, record the material offered, its origin and decomposition state, and traces actually observed. Separate this record from a nutritional recommendation.
Reproduction and young
The marked difference between young and adults makes life-stage records useful. [1] However, the two sources establish neither a number of young per female nor a captive development time. Photograph the first visible young with a scale and compare them with identified adults; do not assign an exact age from size alone.
Observing without forcing detachment
The German profile describes initial immobility and the difficulty of lifting a flattened animal. [2] Prefer observation on its support to trying to detach it. The log can distinguish spontaneous activity, escape, a glimpsed moult and shelter changes. A period without observation must remain described as such, especially when shelters have not been inspected.
Checklist
- Distinguish adult and juvenile photographs.
- Retain the shelter’s damp context.
- Do not assign a subspecies from colour.
Observations to record
- Visible life stage
- Location and shelter
- Activity and identification characters
The app provides individual animal records. Check which features are available for your animal in the released version.
Sources
Document-based overview; not a substitute for veterinary advice.
- British Myriapod and Isopod Group — Oniscus asellus ssp. asellus
Source accessed - Senckenberg / Bodentier⁴ — Oniscus asellus
Source accessed