In my anecdotal experience of hunting for slug caterpillars over a six to eight week period this summer, the Nason’s slug (Natada nasoni – Hodges #4679) was by far the most abundant that I came across. This was particularly true in the drier, oak/hickory/pine hillsides of Hickory Canyon N.A. in Sainte Genevieve County.
This species is able to retract its spines, elongating them to their fullest with any notion of danger. These guys have pretty substantial spines and because the cats were so abundant, I found I was accidentally stung a few times while lifting vegetation. This was not a pleasant experience.
I really enjoy the colors and patterns this species displays.
The image below was one that I had previsualized and worked a good bit on to get it right. I used my plamp to hold the leaf and attached the plamp to a dead limb to position the leaf high enough to get the leaf and caterpillar back lit by the sun. I then used just a bit of flash to illuminate the ‘face’ of the caterpillar and the underside of the leaf. In cases where I removed the leaf to get a photo, I always placed the leaf securely back on the same plant.
-OZB
A Thousand Acres of Silphiums 
Truly a beautiful species! 🙂
The last photo is just brilliant. The subject can’t be anything but massive, ominous, looming, and all-consuming. Such a clever and effective way to highlight the secret life of an overlooked species.