Aglaoctenus castaneus

Males have a total length ranging from 11.9 to 20.1 mm, while females are larger at 14.2 to 24.0 mm in total length. Males can be distinguished from the related species A. lagotis by their wider median apophysis and more conspicuous base of the cymbium in the male palp, as well as by leg-carapace ratios lying between 2.2 and 2.9. The male carapace is orange with a red cephalic region and a clear orange median Y-shaped band. The abdomen is dark gray with a red anterior dorsal spot. Females have a brown carapace with a dark brown cephalic area that is laterally red, and a grayish abdomen with a dark folium pattern. Female epigynes are characterized by a T-shaped septum that is shorter longitudinally and wider transversally compared to A. lagotis, with a more pronounced convex projection in the center. Coloration varies considerably across the species' range, from red to dark, almost black. Amazonian specimens are usually darker, and males show a more conspicuous red spot on the abdomen compared to specimens from other localities.

== References ==

A. castaneus has been recorded from Ecuador, northern Peru, and northern, northeastern, and southeastern Brazil. Additional records suggest it may also occur in Argentina.