I spent time going through Cranshaw's "Garden Insects of North America" chapter on leaf eating insects. Although it didn't look exactly right, I was leaning towards a white-lined sphinx caterpillar.
I watched the caterpillar eat its way up, down, and all around the dogwood. On June 17 I looked and looked through the plant and found no trace of the critter. I checked the surrounding area thinking maybe it fell off a branch but found nothing. My assumption was that it decided it was time to pupate and was somewhere in the soil.
Yes, wonderfully hidden under the foliage was another white-lined sphinx caterpillar--the same but different. This one had different markings and was larger. Both had the distinctive feature of the caudal horn on the posterior part of their body. I tracked the critter daily. One day it was stretched the length of the branch and I was able to measure it at over 3.75 inches.
The moth, Hyles lineata is a color combination of dark olive-brown, silver-gray with streaks of creamywhite, deep pink and black.
I have had my fair share of experiences with damage to my tomato plants by the tomato hornworm. When I saw the posterior horn on the first caterpillar, I panicked as that is one of the tell-tale signs of a tomato hornworm. The major difference is the tomato hornworm is bright green with 7-8 V-shaped white lines on their back, plus they are much larger than either of my caterpillars could hope to be. Their Latin name is Manduca quinquemaculata.
Be sure to listen to the Gardening: Get Good at It "Small Space Gardens" segment on Tues. June 29 on KPOV 88.9 FM between 9-9:30 am.