Probably one or more large hornworms. Look around on the undersides of the leaves above the droppings or nearby until you find a large green caterpillar. You won't need any insecticide, they are large enough to pick off by hand and dispose of.

Here is a link that might be useful: hornworm

I inspected the plants thoroughly and couldn't find any hornworms. Also, there has been no additional damage for two days. Is it possible the hornworms may have been eaten by birds?

Also, the leaves on several of the plants are begining to curl up. Is this related, and what's causing it? Help would be much apreciated.

Also, the leaves on several of the plants are begining to curl up. Is this related, and what's causing it? Help would be much apreciated.

Hello lifemaga

It maybe that your curling-leasves, would be related to the hot weater, or the need for water and will not be related to hornworms.

I will be praying for ya!!!!

mrsjustice

Hello.
These caterpillars even in large size is sometimes difficult to spot if you don't pay attention very much especially just looking throughout your plants. You obviousely see markings of bitings by it/them but you don't see it/them. At night, they tend to go up to the top of your plants and look for another opportunity....travel to the other plant around it.
In my case, 10, 11pm at night, it/they'd be somewhat easier to spot. Downside is by the night, they'd be done some damages already.
Oh, and just in case you see really huge one hunging on top of your plant upside down, don't pick it/them up by your bare finger!
I've just tried to pick up the largest in my life which'd be at least 6 inches long for some reasons!! And worse..it bit my finger as I tried to pick it up and...you imagine the rest especially bitten by a thing you least expect:(
It was pretty bad...if you imagine how they eat plants with their jaws or whatever...
And they try to stick on your finger with back part of their legs or whatever you call them.

From my exp, use a thin bamboo stick and try to shake its head part first then go to its tail part. If you shake it off and it falls on the ground. Your option is just KILL IT! Several times, I let them go..but then they came back even bigger by the time I figured and did much more damage.
I hope this helps. Whatever you do..don't touch them by bare fingers unless you are sure they are small enough:)

While it's possible that the birds ate them, it's kind of unlikely they got to all of them. I ended up spraying my plants with BT (bacillus thurungesis...which I probably misspelled). I just had too many hornworms to keep up with picking them. Besides....even if your hornworms are gone, the moths that lay the eggs that turn into the hornworms are probably not.

The ones I picked off I dropped a patio brick on. There was no place else for them to go. Ordinarily I'd have some sort of mercy, but not this time. I fed a large one to the blue jay--left it on a stick stuck in the back fence, but that's the only one that didn't get squooshed.