Both male and females have long thin brown legs and a distinctive pattern of a large triangular black marking in the middle of the abdomen.

The male copulatory organs have a thin tibial apophysis and lack the triangular lobe on the palpal bulb that other species in the genus possess.

[2] The genus was a member of the tribe Heliophaninae alongside Pseudicius and Cosmophasis, which was absorbed into Chrysillini by Wayne Maddison in 2015.

The oval abdomen is a greyish-russet with white scales forming a fringe on the dark triangular pattern.

Two diagonal white lines cross the edge, running into the dark grey underside.

The copulatory openings lead to straight thick-walled seminal ducts and spherical receptacles.

[13][14] Like other jumping spiders, Mexcala macilenta is mainly a diurnal hunter that uses its good eyesight to spot its prey.

[16] It uses visual displays during courtship and transmits vibratory signals through silk to communicate to other spiders.

[17] The spines on the spider's chelicerae may be used for digging holes to act as underground hiding places.

[1] The female holotype comes from Mkomazi National Park in Tanzania, and was found in 1995 living on a hillside containing Acacia and Commiphora species.

[10] The first example to be identified in Ethiopia was a female discovered in 1988 in Sidamo Province living in a valley amongst Acacia trees.