Other Common Names
Big Poplar Sphinx - name not recommended (see Remarks below)
Explanation of Names
OCCIDENTALIS: occidental means western (as opposed to oriental - eastern); generally refers to the western hemisphere, but in this case refers to western North America
Size
wingspan 108-148 mm, based on Internet photos of several specimens
Identification
Adult: 2 color forms - forewing of light form pale yellowish-brown, darker in median area; forewing of dark form similar to Modest Sphinx (Pachysphinx modesta) but with darker lines that contrast more against ground color
hindwing of both forms with extensive red or pink shading and two short blackish lines near anal angle, the inner line thick and slightly bent but not forming an obvious triangle (as it does in P. modesta)
Larva: head, thorax, and abdomen light green dotted with white; head with converging yellow bands; oblique white band extends from subventral area of A8 to tip of horn on A9; oblique white lines on A1-A7 extend from in front of spiracle to dorsum of adjacent posterior segment; transverse white band at base of anal prolegs
[description by Caterpillars of Pacific Northwest Forests and Woodlands site]
Range
western United States from North Dakota to Texas, westward; in Canada, occurs only in Alberta
Habitat
riparian areas, open parklands, suburbs at low elevations; adults are nocturnal and attracted to light
Season
adults fly from May to September in the south (two broods); June to August in the north (one brood)
larvae present in July and August
Food
larvae feed on leaves of poplar (Populus spp.) and willow (Salix spp.)
adults do not feed
Life Cycle
two generations per year in the south, one in the north; overwinters as a pupa in the soil
Remarks
There is confusion regarding the common name. Holland's 1904 publication, Covell's Guide, and the recent Audubon Guide calls P. modesta the Big Poplar Sphinx but that name is used only for P. occidentalis by the Butterflies and Moths of North America site and several other sources. Since both species are called Big Poplar Sphinx by various sources, it would be less confusing if that name were not used at all, and replaced with either Modest Sphinx (for P. modesta) or Western Poplar Sphinx (for P. occidentalis).
The Modest Sphinx (Pachysphinx modesta) occurs coast to coast in North America, whereas the Western Poplar Sphinx (P. occidentalis) is restricted to western North America.
The Butterflies and Moths of North America site lists this species as occurring in Florida, presumably in error, as only
Pachysphinx modesta [Hodges #7828] appears on the
Florida Lepidoptera list by John Heppner, and none of the 17 records of
P. occidentalis reported by
The Leopidopterists Society are from Florida.
See Also
Modest Sphinx (
P. modesta) forewing is dark greenish-gray in median area, and lines show little contrast against ground color; hindwing has prominent blackish triangle near outer margin; generally found at higher elevations than
P. occidentalis (
compare images of light form and
P. modesta at CBIF)
Internet References
pinned adult images of light and dark forms (Bruce Walsh, Moths of Southeastern Arizona)
pinned and live adult images and live larva image, plus habitat, distribution, description, foodplants, seasonality, and other info (Bill Oehlke, silkmoths.bizland.com)
pinned adult image by Jim Vargo (Moth Photographers Group)
pinned adult image by Paul Opler, plus US distribution map (Butterflies and Moths of North America, butterfliesandmoths.org)
pinned adult image plus common name reference [Western Poplar Sphinx], technical description, similar species, distribution, foodplants (Gerald Fauske, Moths of North Dakota)
live adult images taken in Hereford, Arizona (Larry Line)
live larva image by Jeffrey Miller, plus description, foodplants, seasonality (Caterpillars of Pacific Northwest Forests and Woodlands, USGS)
distribution in Canada - recorded from Alberta only (CBIF)
