Moved from Cixiid Planthoppers.

This was associated with a photo of the adult, taken by the same photographer.

Received e-mails from a few people on this. Here's a couple:

Andy Hamilton - "It's a Fulgoroid nymph, probably Cixiidae as these nymphs feed on the roots of plants and are often found in caves."

Lois O'Brien - "You do indeed have a rare find. It surely is a cixiid nymph-they are known to live in caves in Mexico, Hawaii in lava tubes, and Australia. They are blind, and find each other by substrate stridulation. Hoch and Asche who studied them in Hawaii said the sound was transmitted as far for them as would be a mile for us. They feed on the roots of plants, as the ones who come to the surface as adults, but some become adult in caves. I have seen one adult from California, and one nymph from another cave there."

... that the projections on the side of the head look similar to those seen in some planthoppers?

Can't wait to hear what Dr Hamilton has to say about this one!