Hi I'm just wondering if the caterpillar I found on my lemon tree is poisonous and also what type it is, it's a beautiful red colour but I have never seen one like it and neither have any of my friends that I have shown the pic too. Please help me answer my question.

Thank you

Kind regards, Rachelle

Rachelle. Could you tell us roughly where you are, because not all insects occur in all places and it would help narrow it down, unless someone recognizes it. I just went through a book of caterpillars of eastern North America in case you are in Florida but didn't find anything that looked like it in there.

I need more pix, Giant Swallowtail Butterfly, caterpillar named California orangedogs, is a definite candidate. Caterpillars have several instars where they look different.
Then there is an Orchard Swallowtail...
Could be a sphinx moth, as many of them love citrus. Have never seen these kill a tree, and the poop nourishes the tree as well.

Hi Rachelle and welcome. We really do need to know where you are to ID your caterpillar, so if you could fill in your personal profile (the little blue person icon in the upper right corner) with your city/state that will narrow it down a lot.

I'd call on our resident butterfly expert @mellielong to try for an ID on this guy.

Wow, I don't know but I love him already! It's definitely not a Giant Swallowtail caterpillar. I don't think it's a Sphinx Moth of any kind because they usually have that "horn" on the back side. Let me look around...

I think you will find the orange color means hes abt to change- can you find any that arent orange?

I haven't found him yet and I have to go to bed. Kat, the color does make me think of Spicebush Swallowtails and how they turn orange before they pupate. Knowing where he was found will definitely help us narrow it down.

And FYI, he doesn't look poisonous due to having no visible stinging hairs or anything like that. But I wouldn't touch him until you know for sure. Definitely see if you can find any others that might be a different color.

In addition to where he was found, it would also help to be better able to see the number of prolegs (Rachelle can you get a picture showing all of its legs from the side, not just the front and back ones?). I'm thinking if it had enough prolegs to be a sawfly larva (not a caterpillar) that we'd be able to see that. It does resemble some Geometridae moth caterpillars although I haven't found an exact match. (Different instars are always a problem as Kat noted).

The other thing that would also help is whether it is actually feeding on the lemon, or just hanging out there possibly on the wrong plant.

Sue, it does look like a looper, doesn't it? And I sort of hate admitting this, but the anal prolegs on that thing sure make it look like caterpillar. There, now I've admitted how much I know about caterpillar butts.

I wondered the anal prolegs too, but when I checked it seems that sawflies can sometimes have them. Having said that, it doesn't look like it has the extra prolegs that a sawfly larva would have compared to a caterpillar. Plus the seemingly minimal number of prolegs at the back would indicate a Geometrid moth unless there are more prolegs that the angle hides from view. The latter can be variable in colour too, just to make it more difficult. If we could confirm that the number of prolegs is as they appear in the pics then we'd know we were in the right family at least.