Cisthene plumbea - Hodges#8067
(Lead-colored Lichen Moth).
Photo: 07/13/15, 10 pm.

As the name suggests, the larvae of Cisthene plumbea feed on lichen (algae or cyanobacteria living symbiotically among the filaments of a fungus). The larvae in this genus "are frass shooters that fire their fecal pellets up to 20 times the length of their bodies." 

bug guide (these photos):