This photo of this railroad bridge was taken in Sackville, NB in August, 2011. Shot using a Nikon D7000 with a Nikon 18-200 mm lens (1/125 @ f4.5) and processed using Aurora HDR (using a single RAW image) and Luminar 4.
I debated rotating the image 90° CCW and photoshopping out the thread but it didn’t look natural with the way the caterpillar was curled.
If you look closely, the caterpillar is only touching the wall at the rear of its abdomen, or more technically, its anal prolegs. Other than that, it’s relying on the single thread to keep it from falling down.