Also in 1916, at 19 years old, Paul became the Editor of LORQUINIA. Paul wrote several articles on herpetology and conservation for LORQUINIA in 1916 and 1917. And in 1916-1917, Paul became President of the Lorquin Natural History Club in Los Angeles, which later became the Lorquin Entomological Society. At the end of his term as President, Paul moved to Mexico. While in Mexico, Paul wrote his last article for COPEIA in 1919.
Featured here is the last known article that Paul wrote for COPEIA, which is about Seńor Carlos Cuesta Terrón and his interesting experiments on the behavior of two Horned Lizards in the Valley of Mexico. This article was written when Paul was 22 years old. And this article appears to be the 6th article that Paul wrote for COPEIA in the 4 year period spanning February 1915 to August 1919.
Phrynosoma orbicularia Wiegm. and P. taurus Cope are both abundant in the Valley of Mexico, and specimens of both species when rubbed on the top of the head have time and again been observed to expel blood from the eyes as a result. This experiment, according to Sr. Cuesta is almost invariably successful in the afternoons during the summer, or, in other words, when the animal's sensitivity is warmed up to its greatest intensity by the hottest weather. In the winter, or after long confinement in unnatural surroundings, the lizards rarely respond in the same manner.
The last specimens that Paul sent to the American Museum of Natural History in New York were several snakes and frogs in 1923 and 1924. Sometime later in the 1920s, Paul returned to the United States in New Mexico, where he married Helene Rüthling in 1931. Paul and Helene had three children. The marriage failed, and later, Paul finally resided in Arizona. Paul did return back to Mexico at least once more in 1958, and this time he sent herpetological specimens to the California Academy of Sciences in San Francisco. Paul died in May 1972 at Scottsdale, Arizona, reaching the age of either 74 or 75 years old.