Arachnid · GBIF taxon 2148457
Bull-headed Sac Spider
Trachelas pacificusAlso known as Pacific Sac Spider
Bull-headed sac spiders are prowling nocturnal hunters recognized by their polished reddish-brown carapace and bulbous, pale cream abdomen. Unlike web-building arachnids, they stalk prey on foot across walls, foliage, and leaf litter before subduing small arthropods with robust chelicerae. During daylight hours, they rest tucked inside flattened silken sacs woven into crevices, window frames, or loose tree bark.
NocturnalPredatorSynanthropic
Licensed reference(c) Marshal Hedin, some rights reserved (CC BY) · cc-by
—observations
—countries
—peak records
Not EvaluatedConservation statusIUCN Red List categoriesLCNTVUENCREWEXNot Evaluated — not placed on the risk ladderRed List categories, explained →
Diet & prey
- Silverfish
- Fungus gnats
- Booklice
Predators
- Western fence lizard
- House centipede
- Insectivorous birds
ThreatsHousehold pesticide spraying and habitat loss
HabitatsChaparral, scrublands, residential gardens, and human dwellings
Life span1–2 years
Classification
- OrderAraneae
- FamilyTrachelidae
- GenusTrachelas
- SpeciesTrachelas pacificus
Range data is not available yet.
Interaction riskLow
- Low
- Moderate
- High
- Very high
- Why interaction risk is low
- Bites are rare and trivial; safe to observe at a normal distance.
Responsible observation
- Humane Relocation: Trap wandering individuals beneath an overturned glass and slide paper under to carry outside.
- Daytime Spotting: Check secluded ceiling corners and outdoor bark fissures for their flattened silk retreats.
Look-alike (c) Ilona, some rights reserved (CC BY-SA), uploaded by Ilona · cc-by-sa
Prey (c) Christian Fischer, some rights reserved (CC BY-SA) · cc-by-sa
Close Relative (c) Bill Keim, some rights reserved (CC BY) · cc-by
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