Depends on the species. Tomato Hornworms turn into ONE KIND of Hawkmoth, the Five-spotted hawk moth . Tobacco Hornworms turn into another.Contrary to popular belief, the larvae of hummingbird moths are not tomato hornworms, though they are the same shade of bright green and they have a soft, horn-like spike on their posterior. Instead, their caterpillar’s host foods of choice include snowberry, honeysuckle, dogbane, hawthorn, cherry, blueberry, laurel and viburnum, depending on the species.
Hummingbird moths are friends of the garden. As they sip nectar, they transfer pollen from flower to flower as it clings to their hairy bodies. If you spot one of these fascinating creatures, simply enjoy the show and let it go about its business in peace.
i've not seen many of those here, we've had a number of crops of tomatoes, some years hardly any worms at all or even none. other years i've had to pick off worms and that is ok if i can get them early before they do a lot of damage. it is starting to be the time now where i have to check the tomato plants each morning along with checking the bean plants for the Japanese Beetles. just part of the routine...Btw, most of the hornworms I have seen in the last few years were covered with the white eggs of the parasitic wasp, and their young eat them from the inside out. The one I found last year was close to fast food cup that had water in it. I dropped it in there and found it drowned...for what it's worth.