Top Photo: Elm Sphinx caterpillar on elm.
Each summer I come across a large green caterpillar in an elm tree overhanging the boardwalk in Explore the Wild, an elm sphinx moth caterpillar (Ceratomia amyntor). This species is also known as four-horned sphinx (tobacco and tomato hornworms are sphinx moths). The elm sphinx I see each year is always in the same elm tree, but I’ve never seen the adult, until this spring.
Most adult sphinx moths are cryptically colored in browns, grays, greens, and black. When you’re lucky enough to see an adult sphinx moth of any species during the daylight hours it’s most often clinging vertically and motionless to a plant stem, branch or tree trunk. Though they’re large (wingspan may be over four inches) they can be tough to spot.
The one I spotted was clinging to a tree trunk. Having never seen one before I had to do a bit of research to identify it. It took a while but was the worth effort to scan through photo after photo on a web site called BugGuide.net to find out it was an elm sphinx. Now all I need to do is find the eggs and pupa of this moth to have the entire life cycle in photos.
Sphinx moths may get their name from the way the caterpillars rear back their heads when disturbed, supposedly appearing like an Egyptian Sphinx. The name “hornworm” comes from the fact that most species have a spike-like projection on abdominal segment 8 of the larva or caterpillar. The four-horned sphinx has four additional “horns” on and just to the rear of the head (see top photo).