In the described male and female, the dark brown abdomen has lighter round patches.
The rear edge of the abdomen is usually indented. The legs are light brown with darker rings.
Madagascarchaea lotzi is a small spider with elongated jaws and a small downward-pointing spine near their base. The described male holotype was less than two millimetres long.
The species received its name in 2018. Some Ranomafana National Park specimens had previously been included in Eriauchenius jeanneli. Comparison of the male pedipalps distinguished lotzi by a shallower division in the embolus and the absence of a large terminal division in its posterior portion.
The male holotype had been collected on 18 April 1998, 2.3 kilometres north of Vohiparara village at 1,100 metres. Re-examining preserved material revealed a distinct species within the montane forest fauna.
An extinction-risk assessment has not been added yet.
Madagascar National Parks identifies selective logging, bamboo collection and gold mining as pressures on Ranomafana. It reports patrols, ecological monitoring and reforestation through a 2017–2022 project. Surveys of montane forest vegetation and dead-foliage clumps could help document this spider’s occurrence.