Fauna Spotters logo

Carnarvon Shield-backed Trapdoor Spider (Idiosoma incomptum)

The Carnarvon shield-backed trapdoor spider is a Western Australian species recorded from the Carnarvon area and the near-coastal Carnarvon, Geraldton Sandplains and Yalgoo bioregions. It is listed as Priority 3 by DBCA, a priority category rather than a threatened species listing under the Biodiversity Conservation Act 2016. This means it is poorly known, known from several locations and not considered under imminent threat. Treat possible burrows cautiously during site works.

Conservation status

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

Seasonal planning

Seasonal activity and breeding information for I. incomptum are unknown. Plan surveys and precautionary controls around the works schedule rather than assuming a low-risk season.

Species-specific timing: Not documented.

Planning approach: Use precautionary searches and stop-work procedures whenever suitable ground is to be disturbed.

Month-by-month species activity is unknown. The row is a general planning reminder, not a statement of seasonal biology.

  • Survey and disturbance precautions: General planning window only. Species-specific seasonal activity is unknown; apply precautions throughout the works period.

Identification: Appearance and size

Identification information for this species is limited. Do not rely on size or burrow appearance alone to confirm an identification.

The species belongs to the shield-backed trapdoor spiders. The original description notes small abdominal sigilla and a largely unsclerotised abdomen; the name incomptum refers to an unadorned appearance.

No body-size, colour or other field-level diagnostic measurements are recorded.

Identification: Similar species and field signs

Field characters for distinguishing this species from other Idiosoma are not documented. Record photographs and location details, and seek specialist confirmation where identification matters.

A burrow may indicate a trapdoor spider in general, but no species-specific burrow entrance or other field sign is described for this species.

Distribution: Known range

Records indicate a restricted, near-coastal Western Australian range, but the species remains poorly known.

The species is reported from the Carnarvon, Geraldton Sandplains and Yalgoo bioregions, with Carnarvon given as the type locality.

Atlas of Living Australia records show nine Western Australian records at six distinct 0.1-degree locations, between latitude 24.4 and 27.3 degrees south and longitude 113.5 and 114.2 degrees east. Records outside Western Australia were excluded as likely errors.

Distribution: WA region and status

The DBCA priority fauna list flags the Midwest region. The species is listed as Priority 3: poorly known, known from several locations and not under imminent threat.

No national listing is recorded.

Habitat: Recorded setting

The broad distribution is known, but habitat use within sites is poorly documented.

Records are described as near-coastal and fall within the Carnarvon, Geraldton Sandplains and Yalgoo bioregions. The vegetation communities and landforms occupied have not been identified.

Habitat: Site-level uncertainty

Soil type, moisture conditions, ground cover and associations with particular plant species are not documented. Do not assume that apparently similar parts of a site are either occupied or unoccupied.

Foraging habitat: Diet

Species-specific diet and foraging habitat have not been documented.

The spider's diet is unknown.

Foraging habitat: Implications for works

Do not use assumed prey types or feeding locations to decide where the species may occur. Retain and inspect suitable ground habitat cautiously where it falls within the known range.

Breeding habitat: Known information

Breeding sites, timing and reproductive details have not been documented for this species.

The breeding season, egg or brood details, and where females lay eggs are unknown.

Breeding habitat: Precaution

Do not schedule disturbance on the assumption that any particular season is free of breeding risk. Treat potential shelter sites carefully throughout the works period.

Sheltering habitat: Burrows

Burrowing is described for Idiosoma generally, but species-specific shelter details are poorly known.

A genus-level account describes Idiosoma spiders as digging burrows. It does not establish the depth, entrance form or construction of burrows made by I. incomptum.

Sheltering habitat: Field precaution

As general trapdoor-spider practice, look carefully for possible burrow entrances before clearing or moving soil. Do not excavate an uncertain burrow to confirm its occupant.

Threats: Species-specific evidence

The species is poorly known, and specific threats to its populations have not been identified.

The 2018 taxonomic paper considered I. incomptum data deficient for conservation assessment. It does not provide a species-specific account of threats or population trends.

Threats: Status context

The species is not considered under imminent threat.

Survey methodology: 1. Desktop assessment

Survey methods specific to I. incomptum are not documented. Use targeted, non-destructive searches and report uncertainty clearly.

Check the proposed disturbance footprint against the known near-coastal range and the Midwest region flag. Review available fauna records and previous survey information, while recognising that sparse records do not establish absence.

Survey methodology: 2. Field search and records

As general practice for trapdoor spiders, inspect the ground surface carefully for possible burrow entrances in areas due to be disturbed. Avoid probing or opening burrows.

Map and photograph potential signs with scale and location details. Record survey effort, conditions and areas not searched, and refer uncertain identifications to an appropriate spider specialist.

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: Sandy soils or sand

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

The Carnarvon shield-backed trapdoor spider is a Western Australian species recorded from the Carnarvon area and the near-coastal Carnarvon, Geraldton Sandplains and Yalgoo bioregions.

Automatically indexed from existing profile text. Not a verified preference, mapped occurrence or habitat requirement. Check the original source and regional qualifiers before use.

Evidence: Unreviewed profile-derived candidate

Confidence: Not independently verified

Region: Scope as described in the quoted profile text; not independently verified. Profile states: WA.

Habitat use: general

Attribution gap: No sentence-level reference is attached to the original profile block. Review the profile bibliography; this candidate is not source-verified.

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. Review and plan

Plan around uncertainty: records are few and the species' site-level habitat requirements are not documented.

Check records, proposed clearing boundaries and access routes before works. Have a suitably experienced fauna ecologist assess areas within the known range where ground disturbance is proposed.

Before habitat disturbance: 2. Brief the crew

Explain that possible burrows may be difficult to identify and that the species cannot be ruled out from a lack of obvious signs. Set out a stop-work and escalation process for suspected spiders or burrows.

During habitat disturbance: 1. Work cautiously

Use staged, careful ground disturbance where required, with a clear response if a possible animal or burrow is found.

Keep disturbance within approved limits and avoid unnecessary soil movement. Where practical, have the fauna spotter catcher inspect the active work area as clearing progresses.

During habitat disturbance: 2. Respond to a find

If a suspected spider or burrow is encountered, pause work in the immediate area, prevent further disturbance and contact the project ecologist or fauna spotter catcher. Do not handle or excavate the animal or burrow unless an approved procedure and competent person direct otherwise.

After habitat disturbance: 1. Record outcomes

Document findings and check that disturbance stayed within the approved footprint.

Document searches, possible burrows, confirmed identifications, any animals encountered and actions taken. Include mapped locations and photographs where available.

After habitat disturbance: 2. Review controls

Report any unexpected records to the project ecologist and follow applicable approval and reporting requirements. Review whether work methods or exclusion measures need adjustment before nearby works continue.

Rehabilitation actions: 1. Protect retained ground

Specific rehabilitation requirements for this spider have not been documented. Rehabilitation cannot replace protection of occupied ground.

Keep rehabilitation activities within approved areas and avoid disturbing retained ground that may contain burrows. Prevent unnecessary vehicle movements and soil handling in those areas.

Rehabilitation actions: 2. Restore disturbed areas

Use the project's approved rehabilitation plan and locally appropriate methods. No species-specific substrate, planting mix or restoration target has been established for I. incomptum.

Sources