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Western Pygmy Trapdoor Spider (Bertmainius opimus)

The Western Pygmy Trapdoor Spider, Bertmainius opimus, is a migid spider recorded in Western Australia. Its habitat and ecology are poorly documented, so ground-disturbing works within its recorded range warrant precautionary survey and careful handling.

Conservation status

Western Australia, WA Threatened and Priority Fauna List: Priority 3.

Seasonal considerations

Species-specific seasonal activity and breeding information are undocumented. Plan survey and disturbance precautions at any time of year.

Known seasonal timing: Not documented.

Planning approach: Use precautionary survey and work controls throughout the year.

Seasonal timing is undocumented for this species.

  • Precautionary planning: No seasonal window is known. This is a precautionary planning window only, not a statement of seasonal activity.

Identification: Appearance and size

The species is a spider in the family Migidae, but field marks and measurements are undocumented.

Its colour, body form, distinguishing features and size have not been documented.

Identification: Similar species

Characters for distinguishing this spider from other trapdoor spiders are undocumented. Seek identification support from a suitably experienced arachnologist if a specimen or possible burrow is found.

Identification: Field signs

No field signs specific to Bertmainius opimus are documented. As general trapdoor-spider survey practice, look for possible burrow entrances or doors in the ground, but do not treat these signs alone as confirmation of the species.

Distribution: Known range

Records place the species in south-west Western Australia, but named collection localities are not available.

Atlas of Living Australia records show 27 records in WA at six distinct 0.1-degree locations, between latitude -34.8 and -33.5 and longitude 115 and 116.4. Records outside WA were excluded as likely errors.

Distribution: WA regions

The DBCA list flags the South West and Warren regions. Named sites and information to define a finer distribution are not available.

Habitat: Habitat information

The species' habitat preferences are undocumented.

No vegetation type, soil, landform, moisture regime or microhabitat has been recorded for Bertmainius opimus. Do not assume that a particular habitat feature is required or that apparently modified ground is unoccupied.

Habitat: Site context

For planning, treat terrestrial ground within the recorded WA envelope and the South West and Warren regions as potentially relevant until an ecologist has assessed the site. This is a precautionary approach, not a description of the species' habitat.

Foraging habitat: Diet and foraging

The species' diet and foraging behaviour have not been documented.

Avoid making species-specific assumptions about prey or feeding locations.

Foraging habitat: Precaution on site

During general ground-based checks, inspect the footprint and access routes for possible spider burrows or other signs without disturbing them. This is a general survey precaution and does not establish a foraging area for this species.

Breeding habitat: Breeding information

Breeding behaviour, timing and habitat are undocumented.

No breeding season, mating behaviour, egg production or juvenile development information is available. Do not assign seasonal breeding constraints based on an assumed calendar.

Breeding habitat: Work planning

Where possible, complete suitable survey and ecological review before clearing rather than relying on an assumed low-risk season. This precaution reflects an information gap, not a known breeding period.

Sheltering habitat: Shelter information

Species-specific shelter details are undocumented.

It is not known where Bertmainius opimus shelters or whether it constructs a burrow. The common name identifies it as a trapdoor spider, but does not establish further shelter details.

Sheltering habitat: General search cues

As general practice for trapdoor-spider searches, inspect ground surfaces carefully for possible burrow openings, doors or silk. These are search cues for the group, not confirmed signs of this species. Avoid opening or excavating suspected burrows.

Threats: Known pressures

No species-specific threats are documented.

The species' known pressures have not been documented.

Threats: Disturbance precaution

Clearing and soil disturbance can remove or damage ground features that may be relevant to terrestrial invertebrates. Manage this as a general site risk, not a documented species-specific threat.

Survey methodology: 1. Desktop assessment

Species-specific detectability and survey methods are undocumented. Use a cautious, staged approach and seek expert advice when signs are found.

Check whether the site falls within the recorded envelope and the South West or Warren DBCA regions. Review site history, proposed disturbance and existing ecological information. The records do not identify precise named localities.

Survey methodology: 2. Ground inspection

Have an appropriately experienced ecologist inspect the proposed disturbance area and access routes before works. As general trapdoor-spider practice, carefully examine the ground surface for possible burrows or doors and record their positions without damaging them.

Survey methodology: 3. Identification and records

Do not identify the species from a possible burrow alone. Photograph and map potential signs, minimise handling, and seek arachnological advice if an animal or diagnostic evidence is encountered. Record survey conditions, coverage and any limitations.

Vegetation associations

Source-checked associations and automatically indexed candidates are separated below. An association does not establish site presence, preference or dependence.

No species-specific vegetation association has been indexed or source-checked in this evidence library. This is an evidence gap, not evidence of no association.

Ecosystem associations

Source-checked associations and automatically indexed candidates are separated below. An association does not establish site presence, preference or dependence.

No species-specific ecosystem association has been indexed or source-checked in this evidence library. This is an evidence gap, not evidence of no association.

Soil and substrate associations

Source-checked associations and automatically indexed candidates are separated below. An association does not establish site presence, preference or dependence.

No species-specific soil association has been indexed or source-checked in this evidence library. This is an evidence gap, not evidence of no association.

Water and wetland associations

Source-checked associations and automatically indexed candidates are separated below. An association does not establish site presence, preference or dependence.

No species-specific water association has been indexed or source-checked in this evidence library. This is an evidence gap, not evidence of no association.

Fauna records and mapped habitat: Not yet analysed

Record locations can be overlaid with mapping, but record frequency alone does not measure habitat preference. No species is excluded from desktop assessments by this analysis.

No quality-controlled record-to-map analysis has been completed for this species. The existing generalised distribution dots and indicative range polygons have not been treated as precise occurrence coordinates.

A defensible run needs dated, independently attributable records, coordinate uncertainty, duplicate and captive-record checks, layer versions and regional scope. Preference and absence require additional survey-effort and detection evidence.

Habitat limitations and contrary evidence: No supported exclusion recorded

Not recorded is not the same as cannot occur. Low suitability, resident habitat, breeding habitat and occasional movement are different conclusions.

This library has not established a vegetation, ecosystem or soil-type exclusion for this species. This does not mean all habitat is suitable; the evidence needed to justify an exclusion has not been assembled.

Habitat limitations and contrary evidence: Before using a negative association

  • Confirm the taxon, geographic region, life stage and habitat function covered by the evidence.
  • Check survey methods, season, repeated effort and detectability before interpreting non-detection.
  • Investigate credible contradictory records and microhabitats absent from broad mapping.
  • Do not convert a missing map class, low record count or failed data request into species absence.

Before habitat disturbance: 1. Confirm the footprint

Plan works with the species' habitat and detectability in mind, as both are poorly documented.

Map clearing, excavation, access and laydown areas, and avoid unnecessary expansion into undisturbed ground. Arrange ecological review before disturbance where the site is within the recorded broad WA range.

Before habitat disturbance: 2. Brief the crew

Explain that the spider is a DBCA Priority 3 species and that its field signs are poorly documented. Show workers how to report possible spiders or burrows and who to contact before disturbing them.

During habitat disturbance: 1. Control clearing

Use staged, controlled work and pause locally if a possible spider or burrow is found.

Keep machinery and personnel within the approved footprint. Avoid unnecessary scraping, compaction or excavation outside the area cleared for works.

During habitat disturbance: 2. Respond to a find

Stop work in the immediate area, protect the possible animal or burrow from further disturbance, and notify the site ecologist or fauna spotter catcher. Do not excavate, capture or relocate it unless an appropriately qualified person has assessed the situation and the required approvals and procedures are in place.

After habitat disturbance: 1. Record outcomes

Document findings and review whether work controls were effective.

Document observations, photographs, locations, work pauses and any expert advice. Submit records through the project’s agreed reporting pathway and retain them with the site fauna records.

After habitat disturbance: 2. Review controls

Check whether the disturbance footprint remained within its approved limits and whether any follow-up inspection is needed. Report unresolved identification or handling issues to the project ecologist.

Rehabilitation actions: 1. Restore disturbed ground

Rehabilitation needs for this species are undocumented, so a particular treatment cannot be assumed to recreate its habitat.

Rehabilitate temporary work areas in line with the approved site plan, limiting further soil disturbance and reinstating ground conditions as specified by the project ecologist. These are general site measures, not species-specific habitat prescriptions.

Rehabilitation actions: 2. Monitor and adapt

Record rehabilitation actions and any later observations of possible spider signs. Seek ecological advice before changing ground treatments or assuming the area is suitable for the species.

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