Coremata, including Hair Pencils, is a phenomenon associated with Lepidoptera. They are signalling structures produced by males that are seeking females. They have been proven to transmit pheromones that act as aphrodisiacs and even tranquillisers to females. Further they may act as repellents to rival males.
I have documented this situation before in this blog. The hairs protruding from the abdomen of Syntorarcha iriastis Meyrick, the sound-producing moth, are the Hair Pencils.
Moth of the family Arctiidae seem to be the champions when it comes to the ultimate in bizarre development of Coremata and Hair Pencils. I have seen the phenomena only twice, once on a fieldtrip in the 60's with the late Don MacNeill in California and the other just a few days ago in th Daintree region of far north Queensland.
I have seen many individuals of this moth at night but have never seen it with this display. I was very fortunate to have had my camera handy and not to have stumbled or moved the twig where the male was perched. Even the slightest disturbance would cause him to retract the Coremata.
This moth was described by Linnaeus in 1763. What would he have thought if he had seen it in this juxtaposition?