Hello, beginner_tracy. Let me ask you some questions about your problem. Isolating the pest is important because insecticides will not work against all pests and hydrangeas have few pests.

Where are you located? Do you use chemical insecticides in your garden? Do you release beneficial insects?

Do you know what type of hydrangeas are being affected? Oakleaf hydrangea leaves are nice treats for rabbits and deer, for example.

Is the damage localized or spread randomly? What shape do the holes have? For example, is damage limited to a certain area of the plant? Do the holes look like half moons?

Are there any pests in the underside of the leaves? Do you see any insects when you inspect at night?

Is the damage increasing daily or do you hardly notice any changes now? Meaning has the pest moved on elsewhere....

Lastly, any chance that you could take a picture of the bush and one leaf (upper and lower side)?

Thanks, Luis

Hi Luis,
Thank you for your willingness to help. Sorry it took me a while to get back to you, but I wanted to check for bugs last night.

To answer your questions - I am located on Long Island, NY. No, I do not release beneficial insects into the garden. I do not use any insecticides at this time. The hydrangeas are "Blue Wave" and of the Big Leaf variety, I am told. I took photos of the leaves but am having trouble uploading them here so I will describe the holes to you - the damage is on several leaves on each of several plants (but not all leaves or all plants are affected) The leaves affected are mostly on the second tier of the plant - the uppermost leaves are fine, but those immediately below seem to be the ones being targeted. Most of the holes are small, just a few centimeters in diameter. They are not half-mmon shaped but circular or nearly circular. From what I can tell over the past few days the amount of damage has not increased much. I inspected the plants very carefully last night and found only a spider-looking thing, with a very pale gray body. Yesterday during the daytime, I saw one small light green catepillar (alomst looked like an inch worm, but with feet.) And finally, one more piece that may or may not be part of this puzzle: across a driveway and half a front lawn I just discovered similar looking holes on my carpet roses today, along with a whitening of several leaves on the carpet rose plants that have holes.
I hope that you can be of some help to me because I would love to keep my garden healthy and beautiful. I have heard that I can also take a leaf into my county's cooperative extension and they may be able to diagnose it as well.

Thank you again for taking the time to help!
Sincerely,
Tracy