Trachelas Tranquillus – Broad-Faced Sac Spider

The Trachelas Transquillus, or broad-faced sac spider is a spider that is native to the Eastern part of the United States, especially in New England. The spider is an outdoor spider and can usually only be found in homes during the autumn months, when temperatures fall outside.

Trachelas Tranquillus Description

The Broad-Faced Sac Spider has a solid colored, darker brown or reddish cephalothorax that is on the shinier side.

The abdomen, lacking of any patterns as well, is usually more of a tan or gray color with a smooth but dull sheen to it.

One of the most telling signs in identifying the Broad Faced Sac Spider is by the legs.

The legs will be tan, brown, or even with a reddish shade to them and the front pair will always be much darker than the back legs.

Trachelas Tranquillus
The broad-faced sac spider. Photography by: Jenilee Whisler – Central Lake, Michigan

The broad-faced sac spider is sometimes confused with the Woodlouse Spider due to its similar appearance.


The body of the adult female will grow to about 3/8 of an inch (10 mm). If the legs are included, they can reach approximately 5/8 of an inch (16 mm) across.

Trachelas Tranquillus Web

The Trachelas tranquillus does not spin webs to catch prey. They are nocturnal hunters and during the day, they will usually spin a web to create a thin cocoon-like sac to hide in. Therefore, its common name sac spider. These are often found in the crease where a wall meets the ceiling or in windowsills.

Bites of the broad-faced sac spider

The bite of the Broad Faced Sac Spider is initially painful and often produces a painful erythema, similar to that of a bee or wasp sting. This is also due to the large fangs of the Trachelas tranquillus. Some people who are sensitive to arthropod venom may experience more severe reactions. Overall, its bite is not considered medically significant.

A broad-faced sac spider submitted by Anne from Fairfax, Virginia

Scientific Classification of the broad-faced sac spider

  • Kingdom: Animalia
  • Phylum: Arthropoda
  • Subphylum: Chelicerata
  • Class: Arachnida
  • Order: Araneae
  • Infraorder: Araneomorphae
  • Family: Trachelidae
  • Genus: Trachelas
  • Species: Trachelas tranquillus

US states where the trachelas tranquillus is found

Trachelas Tranquillus – Broad-Faced Sac Spider range map

As mentioned above, the broad-faced sac spider can be found in the Eastern part of the United States. Mostly in the following states: Alabama, Arkansas, Connecticut, Delaware, Florida, Georgia, Illinois, Indiana, Iowa, Kansas, Kentucky, Maine, Maryland, Massachusetts, Michigan, Minnesota, Mississippi, Missouri, New Hampshire, New Jersey, New York, North Carolina, Ohio, Pennsylvania, Rhode Island, South Carolina, Tennessee, Vermont, Virginia, West Virginia, Wisconsin

Trachelas Tranquillus – Broad-Faced Sac Spider

8 thoughts on “Trachelas Tranquillus – Broad-Faced Sac Spider

  1. Found this spider on a door frame in my house. I sadly couldn’t recognize what kind it was. This is definitely a first time I’ve seen one like this in Hortonville, WI.

  2. I found this spider in my house today. I am assuming, based on your responses above, that this is also a broad-faced sac spider. Is that correct?

    Thanks for your feedback.

  3. I found this little guy in the bathroom at work in Fort Worth, Texas. He’s kinda far from home according to this. I could be wrong but this definitely looks like the ones shown here. Just a lighter abdomen. If anyone can verify please do. I’d love to know what this is.

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