Trachelas tranquillus (Broad-faced Sac Spider)

About Trachelas tranquillus

Taxonomic Hierarchy

→ Kingdom: Animalia
→ Phylum: Arthropoda
→ Class: Arachnida
→ Order: Araneae
→ Family: Trachelidae
→ Genus: Trachelas
→ Species: Trachelas tranquillus

Other Common Names

Broadfaced Sac Spider, Ground Sac Spider, Bullheaded Sac Spider


Author of species name: Nicholas Marcellus Hentz. First year published: 1847, as Clubiona tranquilla.


tray-KEE-luhs tran-KWILL-uhs


Trachelas appears to come from a Greek nickname for the emperor Constantine the Great (274-337 A.D.), τραχηλâς, which means “bull-necked” (Cameron 2005); tranquillus is a Latin adjective for “quiet, calm, tranquil.”

Notable Previous Names

Trachelas ruber
Trachelas tranquilla

Previous family: Corinnidae

Identifying Traits of Trachelas tranquillus


Body length (excluding legs) of adult female ranges from 7-10 mm; adult males range from 5-6 mm.

Female Primary Colors

Male Primary Colors

Eye diagram of Trachelas tranquillus


Total of eight eyes. When viewed from the front, two horizontal rows of four. Posterior row is wider than anterior row. Eyes evenly spaced within each row.


First pair of legs thickest, longest, and reddish brown; succeeding pairs of legs increasingly thinner and paler. Third pair shortest. All legs are rather smooth and shiny looking, but are covered with tiny hairs not visible to the naked eye. Tip of each leg has 2 claws.


Rather robust, abdomen scarcely larger than cephalothorax. Carapace deep reddish brown. Abdomen cream to pale gray.

Range of Trachelas tranquillus

Trachelas tranquillus can be found in the following states, provinces and territories across the United States and Canada. Our current understanding of each spider's distribution is drawn from numerous scientific publications and online spider submissions, in order to be as accurate as possible. It is important to remember that spiders do not adhere to the territorial lines decided on by humans, therefore these ranges are subject to change.

Important Range Notes

Keep in mind that there are at least 7 other North American species in the genus Trachelas that look incredibly similar to Trachelas tranquillus, so if you find a look-alike outside of the range listed below, chances are, it is an entirely different species. Only an exam under a microscope can tell them apart.

United States


Additional Information


Prefers warm and dry places, at the base of plants or under stones or leaves, sometimes on trees or fences. Often found in silken retreats constructed in rolled-up leaves or occasionally under rocks. It frequently strays indoors in autumn.


This is a hunting spider that does not spin a web for prey capture. It does use silk for the construction of egg sacs, retreats, and safety lines, though.


Mature spiders are most noticeable in fall because they frequently stray indoors. Most mating takes place in summer and early fall.


Prey is insects and other small animals that the spider can overpower without the aid of a web.


This species is most active at night, as it hunts for prey. It may spend the daylight hours under leaf litter, tree bark, or sometimes in a silken retreat inside a rolled-up leaf. Male spiders typically reach maturity in mid-summer and mate thereafter. Adult females can be found all year round, even in winter. Females produce a white, lenticular egg sac in summer or fall, usually under loose tree bark or under a rock. The package is roughly 10mm in diameter and 2.5mm thick, containing about 30-50 eggs.


This spider can be mistaken for the Woodlouse Hunter, Dysdera crocata. The Woodlouse Hunter can be distinguished by its very long jaws and fangs, as well as its unique eye arrangement. Both spiders can wander into homes on occasion. Trachelas is a member of the family Trachelidae, whereas Dysdera belongs to the family Dysderidae.

Pictures of Trachelas tranquillus


Female Spiders

Male Spiders

Filtering options are grayed out when we do not have pictures for the given perspective. If you are a spider photographer, you can submit pictures of spiders to help fill any voids in our ever expanding library.
  • Trachelas tranquillus
  • Sex: FemaleFemale
  • Maturity: Adult
  • Attributes: Lateral
  • City/Region: South Deerfield
  • State: Massachusetts
  • Country: United States
  • Trachelas tranquillus
  • Sex: FemaleFemale
  • Maturity: Adult
  • Attributes: Dorsal
  • City/Region: Boxborough, Middlesex County
  • State: Massachusetts
  • Country: United States
  • Trachelas tranquillus
  • Sex: FemaleFemale
  • Maturity: Adult
  • Attributes: Ventral
  • State: Washington, D.C.
  • Country: United States
  • Trachelas tranquillus
  • Sex: FemaleFemale
  • Maturity: Adult
  • Attributes: Eyes
  • State: Washington, D.C.
  • Country: United States
  • Trachelas tranquillus
  • Sex: MaleMale
  • Maturity: Adult
  • Attributes: Lateral
  • State: New Jersey
  • Country: United States

References and Further Reading

Various Research Papers

Scientific Diagrams and Keys for Identification

References for the Casual Reader

Species guide last updated: May 30, 2016

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