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Geraldton Sandplain Shield-backed Trapdoor Spider (Idiosoma arenaceum)

The Geraldton Sandplain shield-backed trapdoor spider is a Western Australian spider in the genus Idiosoma, recorded from the Geraldton sandplains. Its species-specific habitat and field-identification details are limited, so survey and clearing work should allow for inconspicuous burrows. It is listed as DBCA Priority 3, a priority category rather than a listing under the Biodiversity Conservation Act 2016. No national listing is recorded.

Conservation status

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

Seasonal planning

Species-specific activity and breeding months are not documented. Use year-round planning precautions rather than assuming a low-risk season.

Breeding period: Not documented.

Survey timing: No species-specific seasonal survey window is documented.

Months show a year-round planning window, not documented activity or breeding months for this species.

  • Survey and disturbance planning: Planning window only. Species-specific seasonal activity is not known; apply survey and encounter precautions throughout the year.

Identification: Appearance and size

Field-identification information for this species is limited. Treat uncertain observations as requiring expert confirmation.

This is a shield-backed trapdoor spider in the genus Idiosoma. Its appearance and size are not described in detail.

Idiosoma spiders are described as having a hardened abdomen with a flattened end and deep grooves along the sides. These traits alone are not a complete diagnosis for this species.

Identification: Similar species

Other Idiosoma species occur in Western Australia. There is no field key or species-specific information here for separating I. arenaceum from them.

Identification: Field signs

A burrow may be a useful survey sign for shield-backed trapdoor spiders, but the entrance, lid, dimensions and other field signs of I. arenaceum have not been described. Record signs carefully and seek specialist identification rather than relying on burrow appearance alone.

Distribution: Known range

The known range is in Western Australia, with records associated with the Geraldton sandplains and the Midwest region.

The species is reported from the Geraldton sandplains of Western Australia. Atlas of Living Australia records show 23 Western Australian records at 12 distinct 0.1-degree locations, between latitude -29.2 and -27.3 and longitude 114 and 115.8. These figures describe a broad record envelope, not precise site locations.

Distribution: WA regions and status

The DBCA list flags the Midwest region. The species is listed as Priority 3, meaning it is poorly known and known from several locations, but is not considered under imminent threat.

Distribution: Site checks

The broad range and record envelope do not confirm presence or absence at an individual development site. Check current records and habitat mapping for the project area, then assess suitable areas in the field.

Habitat: Recorded setting

The species is associated with a sandplain region, but its preferred site-level habitat is not documented.

The species is reported from the Geraldton sandplains. Specific vegetation communities, soil properties, landforms and moisture conditions are not documented.

Habitat: Assessment limits

Do not assume that every sandplain area is occupied or that apparently modified ground is unsuitable. Treat potential habitat within the known range as requiring assessment where works may disturb the ground.

Foraging habitat: Diet and foraging

The species' feeding ecology and foraging habitat are not documented.

What I. arenaceum eats, where it forages and whether it leaves its shelter to forage are not documented.

Foraging habitat: Worksite implications

Avoid removing or disturbing suspected spider shelters while searching for feeding signs. Prey-based surveys or habitat inferences cannot be made for this species.

Breeding habitat: Known information

Breeding biology and timing are poorly known.

Courtship, egg laying, young, breeding sites and breeding season have not been documented for this species.

Breeding habitat: Precaution

Do not schedule works on the assumption that the species has a known breeding-free season. Apply the same survey and disturbance precautions throughout the year unless reliable site-specific evidence supports another approach.

Sheltering habitat: Burrow information

The form and placement of this species' shelter are not documented.

Idiosoma spiders are described as digging burrows. The burrow depth, entrance, lid and microhabitat of I. arenaceum are not documented.

Sheltering habitat: Search carefully

As a general practice for trapdoor spiders, inspect the ground surface closely for small or inconspicuous burrow signs and avoid probing, opening or stepping on suspected burrows. Record their position and seek advice from a suitably experienced arachnologist.

Threats: Status and evidence

The species is poorly known, recorded from several locations and not considered under imminent threat in the current DBCA listing.

A 2018 taxonomic paper stated that the species was not then considered of conservation concern. Neither this assessment nor the current listing establishes the condition of a particular population or site.

Threats: Project risks

Species-specific threats have not been identified. Ground disturbance could affect an animal or shelter if present, so assess and manage risk at the project site rather than assuming occupancy or absence.

Survey methodology: 1. Desktop assessment

Survey planning should recognise that the species is poorly known and that burrow checks are recommended for Idiosoma conservation work.

Review current DBCA information, project-area records and the known Geraldton sandplains range. The broad Atlas of Living Australia record envelope should not be used as a site-level distribution map.

Survey methodology: 2. Ground inspection

Rix and colleagues recommend rigorous surveys for burrow presence or absence for shield-backed trapdoor spiders. As general group practice, inspect suitable ground systematically, including small surface features, and map possible burrows without opening or damaging them.

Survey methodology: 3. Records and identification

Photograph and georeference potential signs, record survey conditions and effort, and distinguish confirmed identifications from unverified burrow records. Obtain specialist advice where identification is uncertain.

The taxonomic paper recommends developing non-lethal, non-destructive methods for obtaining genetic material from wild animals. Do not collect or handle specimens without the required approvals and an appropriate protocol.

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 Geraldton Sandplain shield-backed trapdoor spider is a Western Australian spider in the genus Idiosoma, recorded from the Geraldton sandplains.

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. Plan the work

Resolve survey and avoidance arrangements before clearing begins, as site-level habitat requirements are not established.

Have a suitably experienced ecologist review the proposed disturbance footprint and known records. Plan field checks for areas within the known range where ground will be disturbed.

Before habitat disturbance: 2. Mark and brief

Map and clearly mark any confirmed animals, potential burrows and areas set aside for further assessment. Brief clearing crews on the possibility of inconspicuous burrow signs and the stop-work and notification process.

During habitat disturbance: 1. Clear carefully

Use staged, observant ground disturbance and a clear response process for unexpected spider or burrow encounters.

Keep clearing within the approved footprint and follow any marked avoidance areas. Where practicable, work progressively so that fauna personnel can inspect the active work area.

During habitat disturbance: 2. Respond to finds

If a possible I. arenaceum or burrow is found, pause work in the immediate area, protect the feature from trampling or machinery, and notify the project ecologist. Do not dig out, crush or relocate a spider without an approved method and appropriate expertise.

After habitat disturbance: 1. Record outcomes

Document what was encountered and whether planned avoidance and survey measures were effective.

Log survey effort, mapped burrow signs, confirmed identifications, encounters, work pauses and any fauna actions. Clearly label uncertain records as unconfirmed.

After habitat disturbance: 2. Review next stages

Before further work in comparable ground, review the records and adjust survey or avoidance measures where needed. Report findings through the project's agreed regulatory and fauna-management channels.

Rehabilitation actions: 1. Restore disturbed ground

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

Rehabilitate disturbed areas in line with the approved project plan, using suitable local materials and methods where specified. Do not claim that rehabilitation will recreate occupied habitat unless monitoring supports that conclusion.

Rehabilitation actions: 2. Monitor and learn

Where the project plan requires monitoring, record ground condition and any signs of trapdoor spider burrows using non-destructive methods. Use results to inform later works and rehabilitation decisions.

Sources