Micrathena crassa

Micrathena crassa is a medium-sized orb-weaver spider with distinctive spiny projections on its abdomen. Females have a total length from 5.0 to 7.7 mm, with a carapace measuring 2.3 mm long and 1.9 mm wide. The carapace and legs are orange-brown in coloration. The abdomen is notably spiny, with white coloration and dark brown sclerotized areas on the sides and posterior portions. The dorsum features white areas with spines, and there are typically four pairs of dorsal spines arranged on the abdomen. There is a distinctive groove between the head and thorax regions, and the abdomen may have small anterior lobes above the carapace. Males are smaller than females, with specimens from Peru showing a total length of 4.4 mm and a carapace length of 1.8 mm. Male coloration differs slightly, with a dark olive-brown carapace that is darker on the sides, and whitish coxae and legs. The species can be distinguished from related Micrathena species by its spination pattern and the deep groove across the carapace.

M. crassa has been recorded from Costa Rica south to Argentina, including Venezuela, Colombia, Ecuador, Peru, and other South American countries.