Big Poplar Sphinx Moth
syn. Modest Sphinx

Pachysphinx modesta (Harris, 1839)
Family:  Sphingidae
Subfamily:  Smerinthinae
Tribe:  Smerithini
Hodges # 7828
Phlogenetic Sequence Number 227775

Home    Butterflies    Details     Adult     Adults after Emerging

First Instars on 27 July 2014 -  8 mm long
1st instar -003 

First Instars on 27 July 2014 -  8 mm long

29 and 30th of July 2014 they molted to 2nd Instar
11 mm long
2nd instar 001

#1 Molted to Third Instar 3 August 2014
Photo taken 6 August 2014

#1 Fourth Instar - 9 August 2014
4th -001

#1 Fourth Instar - 9 August 2014
25 mm long
4th _002

#1 Molted to Fifth Instar afternoon of 18 August 2014
5th face_001

#1 Fifth Instar Feeding on Willow- 19 August 2014
5th _2024

#2 Molted to Fifth Instar 20 Augusst 2013 - 45 mm long
Photo on 23 August 2013
#2 5th_002

Photo on August 31, 2014
Fifth instar back began turning from green to brown 30 August  2014

Photo on August 31, 2014 - close-up on back
Fifth instar back began turning from green to brown 30 August  2014

turning brown

#1 Burrowing into Peat, Sand, Sawdust Mixture to Pupate

1 - Male - 52 mm, 2 - Male - 47 mm, 3 - Female - 47 mm
pupae 1,2,3

#1  Male- fourth segment from wing case
#1 4th segment

#1 - Male antennae
#1 antennae

#2- Male 4th segment from wing case
#2 4th segment

#2 Male -antennae
#2 antennae

#3 Female - Fourth Segment interrupted with a vertical line
4th segment #3

#3 Female - Antennae


Photos   ŠNicky Davis
Bob Mower located a female  16 July 2014 at the Jones Ranch Trailhead (Nebo Loop Road) Payson Canyon, Utah County, Utah and gave some to me to rear. I reared them using Coyote Willow-Salix exigua which they ate with no problems.  I hurt one by trying to move it off the netting material of the lid and it eventually died.  They are hooked onto the surface of the leaf so securely that if you try to move them it will tear  their skin and kill them.  If you need to move one to a new leaf, cut the old leaf around the caterpillar then carefully pin it to the new leaf using an insect pin.  As soon as the caterpillar has moved to the new leaf, you can remove the pin and the old leaf.

First Instar on 27 July 2014 (27 July 8 mm)
Second Instar on 29-30 July 2014 (30 July 11mm)
Third Instar on 3-4 August 2014 - 6 to 8 days
Fourth Instar 9-12 August 2014 - 9 to 11 days (9th August 25 mm)
Fifth Instar on 18-23 August 2014 (45 mm on 23rd)
Burrowing into peat mixture 6:00 P.M. 31 August 2014
Close-up photos to determine the sex of each pupae.  #1 male is 52 mm long, #2 male is 47 mm long, #3 Female is 47 mm long.

On Evening of 30th one larva was showing a change of color from gray-green to green-brown, especially on the top or back. On the afternoon of 31 August #1 walked off the plant and when placed back on, it walked back off.  It made a little spot of purged liquid on the bottom of the container and began to rapidly walk around the bottom of the container.  When touched, it became agitated and swung it's head back and forth. This indicates that the larva is ready to stop eating and find a place to pupate.  Soon after #2 also walked off the plant and became agitated and began rapidly walking around it's container.  A container filled with a mix of peat moss, sand and non-toxic sawdust (used for snake habitat) was prepared by dampening it slightly with water just enough that it wasn't dusty.  Both caterpillars were placed in this container and a lid with ventilation holes in the top was secured. Also, a netting material was placed between the lid and the box. Both caterpillars began walking around the surface, then wiggled their way under the peat moss mixture.
Three days later the last one burrowed into the peat right on schedule. They  prepare an underground burrow and pupate in it then hibernate for the winter.

Reported Host Plants
Aspen or Quakies - Populus tremuloides
Cottonwood (populus)
Coyote or Sand Bar Willow 
- Salix exigua
Range Map

go to top