b.t.w.
Very nice picture!

I also read an article recently which addresses the taxonomic status of the gloveri group (Canadian Paper).

According to the article, Hyalophora gloveri has recently been separated from columbia and elevated once more to "full species status" based on several criteria, incl. range (limited overlap with columbia), compatability (i.e. limited hybridization with nominate columbia) and distinct host affinities which do not include Larix.

Please refer to the following:
An annotated list of the Lepidoptera of Alberta, Canada
"Status is revised for the following taxa, which were previously treated as junior subjective synonyms or as subspecies and are herein raised to species status: ... Hyalophora gloveri (Strecker, 1872)... "

Perhaps more info can be gathered - currently, I do not have access to additional details.

Based on collection records and population studies, gloveri has a much wider blending with euryalus to the west along several points of range contact than it does with columbia to the east. In fact, there are patchy contact points and limited blending between the gloveri group and cecropia along the western Plains (eastern Rockies) ranging from Canada to Texas. It has been suggested that the entire Hyalophora group may consist of several distinct taxa or simply represent a complex polymorphic species...(??...lots of questions yet to be answered)