Henry Parker was a prolific writer. He wrote several books and I have seen a number of articles published under his name in scientific journals. However, I have only seen one article about an insect (or an invertebrate of any kind, for that matter) besides the description of the Poweshiek Skipper. This is it.
Henry Webster Parker, “Note on Deilephila Lineata, Fabr,” Psyche, vol. 3, no. 97, pp. 342-342, 1882. doi:10.1155/1882/83987
This is a photo I took earlier this year of the white-lined spinx, Deilephila lineata