Scat or chrysalis?
Hi- this is caterpillar scat. The insect was probably feeding on plants sitting on or overhanging the deck. Are there tomatoes on the deck? It looks a lot like hornworm droppings.
Thank you! Yes, this was just near our tomato plants growing in containers. Any idea of what we should do with hornworms?
Here is our page on hornworms, including information on their control: https://extension.umd.edu/hgic/topics/tobacco-tomato-hornworm-vegetables
The good news is that they are often controlled naturally by a small wasp. If the hornworm has been parasitized, it will look like it has rice sticking out of it, as shown in the link above. Leave those. They will soon die.
Otherwise, they can be brushed/picked off and put in soapy water.