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Northern Shield-backed Trapdoor Spider (Idiosoma clypeatum)

The Northern Shield-Backed Trapdoor Spider is a Western Australian shield-backed trapdoor spider described in 2018. It is recorded from the Murchison and Yalgoo regions, but its habitat and ecology are poorly documented. Works within its range should use precautionary survey and clearing practices. It is listed as DBCA Priority 3 in Western Australia.

Conservation status

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

Seasonal guidance

Seasonal activity and breeding periods have not been established. Use year-round precautionary planning rather than treating any period as low risk.

Activity and breeding: Species-specific seasonal information has not been recorded.

Planning: The row below is a general precautionary planning window, not a documented activity period.

No month-specific activity, breeding or movement data have been recorded for Idiosoma clypeatum.

  • Precautionary works planning: Planning window only. Seasonal activity and breeding timing are unknown, so apply survey and clearing precautions year-round.

Identification: Appearance and size

Field identification details are limited. Suspected individuals or burrows require expert confirmation.

This shield-backed trapdoor spider belongs to the genus Idiosoma. At genus level, spiders have a hardened abdomen with a flattened rear end and deep grooves along its sides. It is not known which features reliably distinguish this species in the field.

Species-specific body measurements, colours and markings have not been recorded.

Identification: Similar species

Field characters for separating Idiosoma clypeatum from other Idiosoma species are not documented. Range or a suspected burrow alone is not enough to identify a specimen.

Identification: Field signs

Species-specific field signs have not been documented. As general trapdoor spider survey practice, look for burrow entrances and any associated silk or trip-lines. Treat these as unconfirmed signs until identified by a suitably experienced arachnologist.

Distribution: Known range

The species is recorded from inland Western Australia. Individual collection localities are not named.

The species is reported from the Murchison and Yalgoo IBRA regions of Western Australia. Atlas of Living Australia records show 78 Western Australian records from 32 distinct 0.1 degree locations, spanning latitude -29.3 to -26 and longitude 115.2 to 120.7.

Distribution: WA regions and records

The DBCA Priority Fauna List row does not specify any DBCA regions. Murchison and Yalgoo are given in the species account and are not DBCA list regions.

These records indicate a broad recorded range, not that the species occurs throughout those regions or at every development site within them.

Habitat: Habitat information

Preferred vegetation, soils and landforms have not been documented.

Specific habitat associations for Idiosoma clypeatum are unknown. Its regional range does not establish a preferred habitat.

Habitat: Site context

For planning, consider potential habitat broadly across suitable undisturbed ground within the recorded regional range. This is a precautionary approach, not a statement of habitat preference.

Foraging habitat: Foraging information

Feeding behaviour and foraging locations have not been documented.

The species' prey, foraging periods and foraging habitat are unknown. A genus-level account describes prey capture at burrow entrances, but this behaviour is not confirmed for Idiosoma clypeatum.

Foraging habitat: Precaution on site

Avoid disturbing suspected burrow entrances during searches or clearing until their status has been checked. Do not use assumed prey, activity times or foraging distances to narrow survey coverage.

Breeding habitat: Breeding information

Breeding habitat, season and reproductive details have not been documented.

The location of egg sacs or young, breeding timing and clutch size are unknown. A genus-level account gives seasonal details, but these cannot be assigned to Idiosoma clypeatum.

Breeding habitat: Works planning

Do not schedule works on the assumption that any season falls outside the breeding period. Apply the same precautionary checks throughout the year.

Sheltering habitat: Shelter information

The species' sheltering habitat has not been described directly.

Species-specific burrow form, depth and placement are unknown. The genus comprises trapdoor spiders, making burrow entrances a reasonable general search focus, but not a confirmed description of this species' burrows.

Sheltering habitat: Search carefully

Inspect the ground surface and likely shelter features carefully where access and site conditions allow. The absence of an obvious entrance does not confirm that the species is absent.

Threats: Conservation status

Specific threats to Idiosoma clypeatum have not been identified.

The species is listed as Priority 3 on the DBCA Threatened and Priority Fauna List dated 1 July 2025. This is a DBCA priority category, not a listing under the Biodiversity Conservation Act 2016. No national listing is given.

Threats: Threat information

Specific pressures, threat processes and impacts of clearing are unknown. The Priority 3 description states that the species is poorly known, known from several locations and not under imminent threat.

Survey methodology: 1. Desktop assessment

Species-specific detectability and survey methods are not documented. Combine records review with careful ground inspection and expert support.

Check current records, the proposed footprint and nearby habitat within the Murchison and Yalgoo regions. The occurrence summary is broad and does not establish presence or absence at a particular site.

Survey methodology: 2. Ground inspection

As general practice for trapdoor spiders, inspect suitable ground slowly for burrow entrances and related surface signs. Record the location, photographs and condition of suspected signs without damaging or opening them.

Survey methodology: 3. Identification and limits

Seek confirmation from a suitably experienced arachnologist when a spider or suspected burrow is found. No species-specific survey season, detection probability or method for confirming absence has been established.

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. Plan the footprint

Use a precautionary approach because the species is poorly known and site-level habitat requirements have not been documented.

Review records and map the clearing footprint before works begin. Where practicable, avoid unnecessary ground disturbance and retain undisturbed areas around suspected burrows until they have been assessed.

Before habitat disturbance: 2. Brief the crew

Brief spotter catchers and clearing crews on the possibility of trapdoor spider burrows, the need to stop and report suspected signs, and the limits of visual identification.

Before habitat disturbance: 3. Set a response process

Agree in advance who will assess a find, how the work area will be isolated, and who will decide when work can resume. Do not assume the species is absent because no records or signs are found.

During habitat disturbance: 1. Watch the work front

Keep the work area under observation and respond cautiously to suspected spiders or burrows.

Have a spotter catcher or other nominated observer check the active work area for spiders and suspected burrow entrances as clearing proceeds. Work at a pace that allows the ground surface to be observed.

During habitat disturbance: 2. Stop and protect

If a suspected spider or burrow is found, pause disturbance close to the find, keep people and machinery out of the immediate area, and seek assessment by a suitably experienced person.

During habitat disturbance: 3. Handle only with approval

Do not excavate, plug or damage a suspected burrow, or attempt to capture a spider, unless an approved procedure and appropriately qualified personnel are in place.

After habitat disturbance: 1. Record and report

Document findings and maintain controls until the responsible ecologist has reviewed the area.

Record the date, location, photographs, work activity and action taken for each suspected find. Report the observation to the project ecologist and follow applicable reporting requirements.

After habitat disturbance: 2. Review the work area

Have the ecologist review the find and nearby disturbed ground before work resumes in the affected area. Apply any project approvals, fauna management procedures and regulator directions.

After habitat disturbance: 3. Keep records

Retain survey and incident records with project documentation. Do not record an unconfirmed burrow as a verified species record or treat an unsuccessful search as evidence of absence.

Rehabilitation actions: 1. Protect retained ground

Species-specific rehabilitation requirements have not been documented. Focus on minimising further disturbance and following expert advice.

Where practicable, retain undisturbed ground around confirmed or suspected burrows and prevent avoidable vehicle or foot traffic in those areas.

Rehabilitation actions: 2. Restore disturbed areas

Reinstate disturbed ground in accordance with the approved site rehabilitation plan. No species-specific evidence establishes that particular planting, soil treatment or artificial burrows will benefit this species.

Rehabilitation actions: 3. Seek follow-up advice

Ask the project ecologist to determine whether follow-up checks are warranted after rehabilitation. A monitoring period or success measure has not been specified for this species.

Sources