This magnificent moth is the largest hawk
moth in the area, being exceeded in size only by the giant silk moths (Saturniidae),
and is a most powerful and imposing insect. Its tongue (haustellum) is so long
that the pupa has a special compartment for it. The caterpillar feeds on Snowberry.
Hemaris diffinis also feeds on Snowberry,
but, unlike vashti, it does not have oblique stripes, and it never approaches
the huge size of a full-grown vashti. Smerinthus
cerisyi and Paonias excaecatus have
oblique stripes but do not feed on Snowberry and, when full-grown, they have
triangular head capsules. It is many years since I have seen Sphinx vashti,
and I suspect that it is now extirpated from this area.