That depends. Birds would probably think that a good moth since it is a source of dood for them, while most gardeners would probably think it a bad moth sine it will lay eggs that become the larva that eat the plants we want to produce food or flowers.

Where in the world are you. Some moth species are only found in some places, others are found in the eastern US and Canada while others are found only in the western US and Canada

That may be one of the Sphinx moths that feeds on grapes and
Virginia Creeper.

kimmq is kimmsr

How about the tomato/tobacco moth, kimmsr? That would be the parent of the caterpillar that feeds on on tomatoes. ;-)

Knowing where cymraes' garden is situated might help.

floral, knowing where cymraes is located isn't particularly important in this instance. The Tobacco hornworm, Manduca sexta, is found in the eastern part of the country; Manduca quinquemaculata, the Tomato hornworm is typically found west of the Rocky Mountains.

I don't have any doubt that one of those is the moth in question, and that cymraes has been finding those big green caterpillars on his tomato plants.

I don't worry when I see the moths, cymraes, but I sure do keep a close watch on my tomatoes for their eggs and hornworm caterpillars.

I appreciate knowing this is a hornworm moth as we had quite a few hornworms earlier in the summer (my chickens love them!). I will definitely be on the lookout for their eggs and the worms themselves. I'm in the Sierra foothills of CA.

rhizo - if cymraes were on another continent - which was possible - there would be a whole different set of moths. For example - there are no tobacco or tomato horn worms where I garden - nor Japanese beetles, squash borers, locusts, potato beetles, etc. The OP's being in z8 and having a Welsh name made me ask the question.

I should have mentioned in my earlier comment to you that I know that our OP is located in the western US. He/she has posted in the past.

It is a very recognizable moth for me, not easily confused with anything else in this country.

Your point, however, is extremely valid....in most instances it is very important to know the general location of whatever it is that a person wishes to be identified.