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Coolgardie Shield-backed Trapdoor Spider (Idiosoma intermedium)

The Coolgardie shield-backed trapdoor spider is a mygalomorph spider known from south-western Western Australia, including the eastern Avon Wheatbelt and north-western Coolgardie bioregions. It is listed as Vulnerable under the Biodiversity Conservation Act 2016 (WA) from 1 August 2026, and its poorly known distribution warrants careful checks and precautionary handling where works may affect recorded locations.

Conservation status

Western Australia, Biodiversity Conservation Act 2016: Vulnerable.

Seasonal planning

Seasonal activity, breeding and movement have not been documented for this species. Plan surveys and precautionary checks without relying on a presumed seasonal window.

Breeding: No species-specific breeding months are recorded.

Survey planning: Seasonal detectability is not known.

The row is a general planning prompt, not a statement of species-specific seasonal activity.

  • Survey and work planning: General planning window only. Seasonal activity and detectability are not known, so consider checks throughout the year.

Identification: Appearance and size

Identification information for this species is limited. Avoid relying on general trapdoor spider features alone for a field identification.

The species is a shield-backed trapdoor spider in the mygalomorph family Idiopidae. Its description refers to intermediate-sized abdominal sigilla and a relatively unsclerotised abdomen.

No body length, colour details or other field measurements are recorded.

Identification: Similar species and field signs

Several Idiosoma species occur in Western Australia. There is no field key or enough comparative information to distinguish this species reliably from similar species.

Burrows may be a useful general sign when searching for trapdoor spiders, but a burrow alone does not confirm this species. Seek expert identification of any spider or associated material.

Distribution: Known range

Records indicate a south-western Western Australian range, including parts of the Avon Wheatbelt and Coolgardie bioregions.

The reported range includes the eastern Avon Wheatbelt and north-western Coolgardie bioregions. Bodallin is the type locality.

Atlas of Living Australia records show 12 Western Australian records at 10 distinct 0.1-degree locations, spanning approximately latitude -31.4 to -30.1 and longitude 117.7 to 120. These records do not represent the species' complete distribution.

Distribution: WA listing regions

The DBCA priority list flags the Goldfields region for this species. Its distribution should not be assumed to end at an administrative or bioregional boundary.

A 2026 paper reports substantive range extensions for the species, but does not name the additional localities in the reported account.

Habitat: Available habitat information

The species' site-level habitat and preferred vegetation, soil or landform are not known.

The species is reported from the eastern Avon Wheatbelt and north-western Coolgardie bioregions. These regional descriptions do not identify the habitat used at individual sites.

Habitat: Site interpretation

Do not use a presumed vegetation type or substrate as the sole basis for ruling out the species. Treat recorded locations and relevant survey evidence as important even where site habitat preferences are unknown.

Foraging habitat: Species information

The species' prey, foraging behaviour and foraging habitat have not been documented.

No species-specific diet or prey capture observations are documented. Do not infer a prey list from descriptions of other Idiosoma species.

Foraging habitat: General search context

As general guidance for trapdoor spiders, searches can include the ground around any suspected burrow entrance and its immediate surrounds. This is a group-level search approach, not a documented foraging pattern for this species.

Breeding habitat: Breeding information

Breeding habitat, mating behaviour and breeding season have not been documented for this species.

Where and when this spider mates, lays eggs or produces young is not known.

Breeding habitat: Precaution

Do not schedule site works on the assumption that breeding is restricted to a particular season. Where a known or suspected occurrence may be affected, obtain fauna advice before disturbance.

Sheltering habitat: Burrows

Species-specific shelter details are not known. General information about the genus indicates that Idiosoma spiders use burrows.

A genus-level account describes Idiosoma spiders as digging burrows. The burrow form, depth and entrance features of I. intermedium are not documented.

Sheltering habitat: Shelter checks

As general group-level practice, inspect the ground carefully for possible burrow entrances and avoid damaging or probing suspected burrows during initial checks. A burrow should not be attributed to this species without supporting evidence.

Threats: Known status

Specific threats and population trends have not been documented for this species.

The Biodiversity Conservation (Listing of Native Species) (Fauna) Order 2025(2), in operation from 1 August 2026, lists the species as Vulnerable. It was previously Priority 3 on the DBCA Threatened and Priority Fauna List dated 1 July 2025. It is not a listing under the Biodiversity Conservation Act 2016. No national listing is given.

Threats: Threat information

No species-specific threats, impacts of clearing or evidence of decline are reported. Avoid presenting general development pressures as confirmed threats to this species.

Survey methodology: 1. Desktop assessment

Species-specific detectability and survey methods are not known. Use a cautious, documented search approach and seek specialist input.

Check the project area against known records, the reported bioregional range and the DBCA Goldfields listing region. Include the type locality at Bodallin and the Atlas record extent as context, not as proof that unrecorded areas are unoccupied.

Survey methodology: 2. Field inspection

As general practice for trapdoor spiders, inspect suitable ground surfaces closely for possible burrow entrances. Record search effort, conditions, locations and photographs, and avoid damaging suspected burrows.

A species-specific survey season, detection rate or validated survey protocol is not known. Arrange expert assessment where a potential occurrence is found or where habitat disturbance is proposed within the known range.

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. Define the work area

Plan for the species' poorly known site-level distribution and do not assume that a lack of records means a site is unoccupied.

Review available records and map the full disturbance footprint, access routes, laydown areas and other ground disturbance. Commission a suitably experienced fauna specialist to assess potential occurrences where work falls within the reported range.

Before habitat disturbance: 2. Set precautionary controls

Where a potential burrow or confirmed occurrence is identified, obtain specialist advice on avoidance and any required approvals before works proceed. Brief crews on identification uncertainty and the requirement to stop and report suspected spiders or burrows.

During habitat disturbance: 1. Stop and protect

Use a stop-work and reporting response if a suspected spider or burrow is encountered during ground disturbance.

Pause work in the immediate area, prevent further disturbance and do not dig into, fill or block a suspected burrow. Keep machinery and unnecessary foot traffic clear while the find is assessed.

During habitat disturbance: 2. Record and escalate

Notify the fauna spotter catcher or project ecologist. Record the location and circumstances, and take photographs only where this can be done without disturbing the animal or burrow.

Do not handle or relocate the spider unless directed by an appropriately qualified person under the relevant approvals and project procedures.

After habitat disturbance: 1. Assess the find

After a suspected encounter, retain a clear record and do not resume affected works until the find has been assessed.

Have a suitably experienced specialist assess identification and the potential extent of the occurrence. Record the outcome, photographs, coordinates, actions taken and any uncertainty.

After habitat disturbance: 2. Review controls

Review the work method and exclusion or avoidance controls with the project ecologist before restarting. Report and manage the find in accordance with project approvals and applicable procedures.

Rehabilitation actions: Reinstate disturbed ground

Species-specific rehabilitation requirements and habitat restoration outcomes are not documented.

Where rehabilitation is required, follow the approved site plan and avoid unnecessary compaction or further disturbance around recorded or suspected occurrences. Do not create or reconstruct burrows based on assumptions about this species.

Rehabilitation actions: Monitor and document

Record rehabilitation actions and any subsequent observations of spiders or burrows. Seek specialist advice to set monitoring objectives because species-specific recovery or monitoring methods are not documented.

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