A dark (brown/black) rust fungus that is found on a number of lichens, especially those that include Trenthepolia as their photobiont. Arthonia atra is particularly prone so colonies of this lichen should be examined carefully. In isolation it requires microscopic examination but can be more easily recognised if found on the host lichen.

A good image which shows both the fungus and the host lichen.

A lichenicolous fungi found on the lichen Arthonia atra (formerly Opegrapha atra).

All year round.

Fairly common.

Unknown.