Modest Sphinx Pupae Arrive

Our Modest Sphinx pupa (Pachysphinx modesta) have arrived from New Jersey.

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Today we had six Modest Sphinx pupae arrive from a New Jersey source, shown below. Three are female and three are male. The pupae came coated lightly with dirt as the breeder must have allowed the caterpillars to pupate in soil, but we tried to wipe them clean as best we could so we could see the details better. The pupae closely resemble our Smerinthus ophthalmica pupa, which belongs in the same subfamily, Smerinthinae (comparison shown below). The P. modesta are redder and much larger, with slightly wider wings, but almost every other feature are the same. The pupae shape is thick and less tapered than the other two Sphingidae subfamilies. Some of the P. modesta pupae had a few small deformities on the anterior dorsal side, possibly due to the bumpy soil surface. Also, one of the males leaked hemolymph at the cremaster, which was broken off (possibly during shipping), but it is alive and will hopefully survive*. The female and male pupae are not dimorphic as far as we could tell except for a slight size difference; females weighed 4.3, 4.5, and 4.9 while males weighed 3.3 4.3, and 4.4.  However, inspection of the gonophore on the ventral posterior end makes it extremely easy to sex them. The females have semi-merged segments at the end with a single slit on the fourth abdominal segment after the wings, while the male segments are well defined with a pair of small kidney shaped spots on the fifth segment after the wings.

*Update 11/7: the male pupa with the broken cremaster is clearly dead now.

Regarding some background information on the species, Pachysphinx modesta is a very large sphinx moth in the Smerinthinae tribe ranging in much of North America except for the south western United States where it is replaced by P. occidentalis (Western Big Popolar Sphinx), though the two are sympatric in parts of their range. The wingspan of P. modesta is 76-120 mm (3 - 4 11/16 inches) according to Bugguide and BAMONA and are mostly gray except the hindwings, which have a crimson patch. Like other Smerinthinae and Saturniidae, the adults have vestigial feeding organs and are short lived. The caterpillars are like typical Smerinthinae larvae, being green and granulated with a triangular head capsule, but have less elongated bodies. They feed on poplar, aspen, and cottonwood (Populus) and willow (Salix).

This species is univoltine in the north so the pupae are in diapause, meaning we will have to overwinter them until next spring. It gets quite cold where they are originally sourced, so we will have to refrigerate them soon. For now, we just placed them in an airtight container with the rest of our Sphingid/Saturniid pupae. When they close next spring, we plan to pair them to obtain eggs and rear them on willow (Salix) just like we have reared our S. opthalmica caterpillars. 

- Alan