Pachysphinx occidentalis, the Big Poplar Sphinx

Pachysphinx occidentalis occidentalis
(H. Edwards, 1875) Smerinthus

Pachysphinx occidentalis (pale form) by William A. Harding.

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Family: Sphingidae, Latreille, 1802
Subfamily: Sphinginae, Latreille, 1802
Tribe: Smerinthini, Grote & Robinson, 1865
Genus: Pachysphinx Rothschild and Jordan, 1903
Species: occidentalis occidentalis (Henry Edwards, 1875)


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Pachysphinx occidentalis occidentalis, the Big Poplar Sphinx (Wing span: 5 1/8 - 5 7/8 inches (13 - 15 cm)), flies in riparian areas and suburbs from Alberta and North Dakota west to eastern Washington; south to Texas, Arizona, southern California, and Baja California Norte.

Pachysphinx occidentalis female, Silver City, New Mexico,
August 6, 2007, courtesy of David R. Furnas.

There are two color forms: the upperside of the forewings is yellow brown in the pale form and dark gray in the dark form. Lines and bands are well-defined. The upperside of the hindwing has a crimson patch covering varying amounts of the wing, and two dark lines which do not form a distinct triangle.

Pachysphinx occidentalis male, courtesy of Martin Jagelka

Visit Pachysphinx occidentalis, Payson, Gila County, Arizona, July 24, 2009, courtesy of Lauren Paterson.


Male and female Pachysphinx occidentalis moths come to lights as two broods in southern Arizona from May-September, and as one brood northward from June-August. The adults do not nectar at flowers.

Pachysphinx occidentalis, Washoe Valley, Washoe County, Nevada,
June 20, 2012, courtesy of Terri McLaughlin.


Little is known about the eclosions of the earth pupators, but many believe pupae wiggle toward the surface just prior to emergence.

Pachysphinx occidentalis female, courtesy of Martin Jagelka


Female Pachysphinx occidentalis extend a scent gland from the posterior of the abdomen to lure in the night flying males whose large claspers are frequently wide open as they fly in to lights around midnight.


Pachysphinx occidentalis eggs are quite large and a translucent pale green.

Larvae feed on cottonwood and poplar (Populus) and willow (Salix).

Pachysphinx occidentalis male, courtesy of Martin Jagelka

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