Pachysphinx occidentalis

Edwards, 1875

Western Poplar Sphinx, Big Poplar Sphinx

Pachysphinx occidentalis is a large sphinx moth in the Sphingidae, first described by Henry Edwards in 1875. It is notable for its substantial size, with a wingspan of 130–150 mm, and exhibits two distinct color morphs. The has a broad North American distribution and is closely associated with riparian where its larval plants occur.

Pachysphinx occidentalis by (c) Pinnacles National Park, some rights reserved (CC BY), uploaded by Pinnacles National Park. Used under a CC-BY license.

Pachysphinx occidentalis by no rights reserved, uploaded by Robbie Hannawacker. Used under a CC0 license.

Pachysphinx occidentalis ova by Whitney Cranshaw, Colorado State University, Bugwood.org. Used under a CC BY 3.0 us license.

Pronunciation

How to pronounce Pachysphinx occidentalis: //ˌpækɪˈsfɪŋks ˌɑksɪˈdɛntəlɪs//

These audio files are automatically generated. While they are not always 100% accurate, they are a good starting point.

Identification

The large size (130–150 mm wingspan) distinguishes this from most other North American sphinx moths. The crimson patch on the hindwing upperside, combined with the two dark lines that do not form a triangle, separates it from similar species in the Pachysphinx. The two color morphs (pale yellow-brown versus dark gray forewings) are both recognizable by these hindwing markings.

Images

Appearance

Large with wingspan of 130–150 mm. Two color forms exist: a pale form with yellow-brown forewings, and a dark form with dark gray forewings. Both forms display well-defined lines and bands on the forewings. The upperside of the hindwing features a crimson patch of variable extent, accompanied by two dark lines that do not form a distinct triangle.

Habitat

Riparian areas and suburban environments where plants are available. Associated with cottonwood and willow stands along waterways.

Distribution

Throughout Canada and the United States. Specific records from Alberta, Manitoba, and Saskatchewan in Canada. Two recognized : P. o. occidentalis ranging from Alberta and North Dakota west to eastern Washington, south to Texas, Arizona, southern California, and Baja California Norte; and P. o. regalis in Mexico.

Seasonality

Two per year in southern Arizona with active from May to September. One generation per year farther north with adults on wing from June to August.

Diet

Larvae feed on cottonwood (Populus ) and willow (Salix species). feeding habits not documented in available sources.

Host Associations

Populus - larval cottonwood
Salix - larval willow

Life Cycle

Two per year in southern portions of range; one generation per year in northern portions. Larval development occurs on Populus and Salix . Specific details of , pupal, and longevity not documented.

Behavior

have been observed at mercury-vapor and ultraviolet light stations. Attracted to artificial lighting in oak/juniper woodland .

Ecological Role

Larval herbivore on riparian trees; likely serves as though specific interactions not documented. Forms part of insect in riparian and suburban .

Human Relevance

Attracted to artificial lighting in residential areas. No significant economic impact documented; not a pest . Potential ecological indicator for healthy riparian with native Populus and Salix stands.

Similar Taxa

Pachysphinx modestaSimilar size and ; distinguished by hindwing pattern details and geographic distribution
Other SmerinthinaeShared characteristics; P. occidentalis distinguished by large size and specific crimson hindwing markings

More Details

Subspecies

Two recognized: Pachysphinx occidentalis occidentalis (widespread across western North America) and Pachysphinx occidentalis regalis Rothschild & Jordan, 1903 (Mexico).

Light attraction

Documented at mercury-vapor and ultraviolet light stations in southeastern Arizona oak/juniper woodland, indicating activity and attraction to artificial light sources.