The adult white-lined sphinxes do feed; perhaps it was looking for mineral content on the tire.

The moth also could have been roosting there, explaining its lethargy. What time of day and how long had the vehicle been parked there?

It was about 11:00am and vehicle was parked for 2 or 3 hours.

EDIT: had this wrong, corrected below.

This post was edited by bostedo on Fri, Aug 8, 14 at 11:02

Not a typical time for moths to take up roost, but it could have been disturbed from its previous roost and chose the tire, perhaps then in total shade.

Very cool temperatures would also make the moth sluggish.

Thanks - didn't realize they can't fly well until warmed up. It was 50ð f earlier that morning, so probably explains why it had so much trouble getting away. The tire was just coming out of full shade. Its lethargy is what made me think it might be dying, though certainly looked healthy otherwise.

Just did a Google search and found it's not that uncommon for them to roost on car or bike tires. Wonder if they do this on cool mornings knowing the black surface will heat up faster than other options?

Oops.... looked at the wrong "create" date/time; photo was actually taken at 8:45am which would have been when we were first heading out, meaning the moth had probably roosted there over night.

This post was edited by bostedo on Fri, Aug 8, 14 at 11:10

Interesting about the tire roosting, often moths will be found on mostly matching backgrounds, and the white-lined does have a fair amount of dark in it. The camouflage is defeated by the white pattern, though.

Cool temperatures slow down most insects. If your moth finally zipped off after prodding, rather than weakly (for a sphinx moth) flying a few feet, it was healthy. No evidence of great age per bald thorax or wing chips / fading in the photo.

A beautiful moth.