About Aphonopelma marxi (Simon, 1891)
Aphonopelma marxi is typically dark brown to black, very hairy, with patches of orange to red hairs on its abdomen. For mature individuals, the male carapace measures between 8.3 and 10.5 mm (0.33 to 0.41 inches) long; mature females are larger, with carapace lengths ranging from 13.5 to 15.3 mm (0.53 to 0.60 inches). The total body length of a female, including chelicerae, is approximately 35 mm (1.4 inches). A. marxi can be differentiated from other Aphonopelma species that share its geographic range by its dark coloration, generally very hairy appearance, size, and habitat. In males of A. marxi, the ratio of the femur length to the metatarsus length of the first leg is greater than 1.69; this ratio is smaller in similar species. In females of A. marxi, the ratio of the femur length of the first leg to the metatarsus length of the third leg is greater than 1.76, while this ratio is smaller in similar species. One additional distinguishing trait between the sexes is that males have characteristic "hooks" on their first legs, which are used during mating. Aphonopelma marxi is widely distributed across high-elevation areas of the Four Corners region: northern Arizona, northwestern New Mexico, southwestern Colorado, and southeastern Utah. It occurs in a variety of habitat types, including mixed conifer forests and sagebrush steppe. This species is noted as "very common" within this range, but it is hard to locate because it normally stays inside its hidden burrow. Burrows of all species belonging to the Marxi species group are described as "incredibly difficult to find".
