Brachybothrium pacificum Simon, 1884 Antrodiaetus pacificus is a species of mygalomorph spiders native to the Pacific Northwest.

Both male and female were first described by French arachnologist Eugène Louis Simon in 1884 under the name Brachybothrium pacificum.

[2] The specific epithet refers to its geographical distribution along the pacific coast of North America, between San Francisco Bay and Alaska.

[3] Both males and females have a carapace that is dark brown to black, and two to three sclerotized patches on the abdomen.

[3][5] They live in cool, damp forest and build burrows in soft substrates, usually sand, moss, or decaying wood,[3] where they brood their eggs and overwinter.