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Species Page - Pachysphinx modesta
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scientific name    Pachysphinx modesta    

common name     Big Poplar Sphinx

Open mature poplar forest or mixedwood forest with poplar.

Adults are on the wing from mid May through mid July.

A very large moth (10.0-12.0 cm. wingspan) with long, narrow forewings banded with light and dark grey-brown and a maroon hindwing with a blue-black blotch in the anal angle. Nearly impossible to mistake for any other Alberta moth. Very pale specimens from southern Alberta have been called Pachysphinx occidentalis. P. occidentalis is a much lighter tan moth with more extensive maroon shading on the hindwing. However, Alberta specimens appear to grade from pale to dark forms, and all Alberta Pachysphinx are treated here as modesta, pending further study.

life history
Adult Big Poplar sphinx are nocturnal, and come readily to light. The large green larvae are reputed to be the largest insect in Alberta, based on weight. The larval stage extends from mid-July to September, and they overwinter in the ground as pupae.

A common, widespread moth. No concerns.

diet info
No Alberta data. Elsewhere poplars, and in particular aspen poplar. There are also single reports from willow and birch, but these should be confirmed.

Throughout much of North America, from the Gulf States north into the Boreal forest region across Canada. In Alberta, it occurs in cottonwood stands along the rivers of the plains (occidentalis ?) north into the boreal forest at least to Ft. McMurray, and west into the mountains at low elevations.

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Comments (1)Add New Comment

Bonnie (2015-06-08)
I have a Pachysphinx Modesta in a jar on my kitchen table. I understand the adults don't eat so I assume it is just waiting to die. It is a beautiful creature, it flew into my house the other night. I put it outside and it has been sitting on my deck for 2 days. I finally picked it up and put it in a jar, out of the cold, wind and rain. Kind of sad.....

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Specimen Info
There are 71 specimens of this species in the online database
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Specimen List (71)
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