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Pachysphinx. modesta or occidentalis?? - Pachysphinx modesta

Pachysphinx. modesta or occidentalis?? - Pachysphinx modesta
Colorado Springs, El Paso County, Colorado, USA
September 18, 2013
Size: 4" wingspan

David / Bill- thank you both
David / Bill- thank you both for your help!

i saw the ranges overlapped here in CO, so that's what made me wonder.

Your comment came in the middle of my writing,
and somehow it caused it to duplicate instead of updating. Anyway, (deleting the duplicated part) -

- - - except, the ones in the Pacific Northwest (north from Washington and Idaho) tend to be smaller and dark, and are usually put into P. modesta, even though they look somewhat distinct.

My personal gut feeling - they are probably all one species. But, I could be wrong, and that is not how they are treated. Even so, they seem to blend into one-another in the Rockies and in New Mexico.

P. modesta usually isn't as light as yours, but sometime sit is. This one from Ohio is nearly identical:

thanks for all the help
thanks for all the help, really appreciate it!

Highly variable in how well developed,
but pretty constant in how they are arranged. Different authors have different ways to distinguish the two "species", which yield different results, so it can be very confusing. Generally, east of the Rockies and in the Pacific Northwest it is most likely going to be P. modesta, and west from That it will most likely be P. occidentalis. Usually, in P. modesta the bands across the front wing are straighter overall, but may be a bit more crenulate on a small scale. The inner dark mark on the hind wing is supposed to be more distinctly angled on P. modesta, but I have a hard time seeing much of a difference there.

Wonderful - thanks for the de
Wonderful - thanks for the detailed description! (one wonders how real the species truly are, but I'm not going to charging in, collect some, and try and crossbreed them, so I'll have to leave it to speculation)

occidentalis, I think
Based on the narrow dark lines on the hindwing and the less strongly contrasting upperwing, I'd say occidentalis, but other opinions welcome!

The two are often barely distinguishable
but this looks like P. modesta, which is the one that should be on the east side of the mountains in Colorado.

Moved from ID Request.

thanks! so how variable are t
thanks! so how variable are the black markings on the anal wing? i see some variation between the two, are there consistencies?

Also curious here, since I (o
Also curious here, since I (obviously) called it wrong!

Here on PEI in eastern Canada, Pachysphinx modesta is very common.
It tends to be more grey than occidentalis (browner) from out west.
I also report the forewing lines to be more diffuse in modesta, and the am line in modesta is generally vestigial whereas in occidentalis
it is quite distinct. I would not be surprised if the two species have overlapping ranges in Colorado and there may be hybrid or blend zones. My El Paso County page is at
Tuttle reports both species throughout Colorado.
My choice for this species due to browner colour, distinct am line and generally more precise, less diffuse lines would be occidentalis.
Bill Oehlke

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