Cynipidae

Description:

The Mushroom Observer community helped me to realize that this is not a fungi at all, but most likely a wasp gall! Therefore, I have changed my initial thought that this was some kind of cup fungus and have changed the spotting to the appropriate arthropods section. The gall wasps, also known as Gallflies, are a kind of wasp that spends a portion of its life inside of a gall, shown here in the spotting. From egg to adult, they are protected in this most vulnerable part of their life by the structure. Other conventional wasps have taken advantage however of the gall wasps' work and tend to parasitize the gall with an egg of their own species.

Habitat:

Was found on a leaf at around 6,000 feet elevation. There were no similar structure growing on the surrounding leaves or elsewhere within the mountain we were hiking on.