[2][3][4] Adults are typically 4–6 cm (1.6–2.4 in) long, with females growing larger than males.

[3][4] It is reddish brown with black dots on its outer wings, however there is some variation in coloration, with more northern variants tending to be greener, and southern ones more brownish-buff.

Brachystola magna has extremely small wings and is unable to fly.

It overwinters in the egg, which hatch in the spring and reach adulthood in August.

[6] Walter Sutton's description of reduction division was based on studying the spermatocytes of Brachystola magna.