Geotrupes blackburnii: ssp. blackburnii vs. ssp. excrementi

While I look up the references to id my Geotrupes blackburnii collections to subspecies level, I found couple of references(below):

1. https://naldc.nal.usda.gov/naldc/download.xhtml?id=IND84113945&content=PDF
2. http://www.mdentsoc.org/wp-content/uploads/2016/03/MD-Entomologist-book-2013-proof.pdf

I found out that G. blackburnii blackburnii occurs more to eastern states, while the G. blackburnii excrementi occurs more to western states of its whole range of distribution, without overlapping according to the reference #1.

I couldn't find the "key" to distinguish the two, but if they do not overlap in distribution, I think some images of G. blackburnii blackburnii (Texas & Mississippi) should be considered to be moved to different pages. Or is there new reference available regarding to this? If anyone has key information, could you please share and add it to the information page?