It's an "orange dog," the caterpillar of the giant swallowtail butterfly (Papilio cresphontes). If you just have a few, you can pluck them off and crush them. Or you could spray the tree with Dipel or Thuricide or some other material containing Bacillus thuringiensis (BT). But usually there are just a few, so you can pick them off by hand. Or on a large tree, leave them to mature, and you'll have more butterflies in the garden.

I'll add that it's a BABY caterpillar! Just wait until you see what they grow up to be, lol! Of course, the bigger they are allowed to become, the more they will eat.

These caterpillars, though disguised exceedingly well as a big gooey bird dropping, are a favorite treat of predatory animals (including wasps). I've not noticed that birds ignore them while they are still caterpillars...I guess that disguise works too well. However, once they pupate, birds really go after the chrysalises.

I agree with Malcolm. Remove these insects by hand. They don't sting. And look for single, round, pearl-like eggs deposited on the upper side of leaves. They can be removed, too.

I grow seedling citrus in containers strictly for the pleasure of watching the life cycle of the Giant Swallowtails. The gorgeous adults are plentiful in a blooming annual and perennial garden where they will nectar upon a wide range of flowers.

Here is a link that might be useful: Just click for some neat pictures

Rhizzo, absolutely beautiful! Thank you for sharing and those nice pictures.I have never seen a butterfly like that..

Mike..:-)

can't see any bugs...leave are eaten, blossoms falling off, ends of limbs dieing.
two different orange tree varieties but not my tangerine tree.

Wow, my citrus have been outside for a while. I had a a butterfly flying aound my yard today... my orange tree has 2 nibbled leaves...that butterfly looks very much like the one in that picture......

If I had known what it was, I would have put it in a place other than my tree and let them grow into a butterfly! I'm so SAD . however I did cut the branch the little guys were on and put them in the trash. Hope the make it! I'mgrowing a garden specifically for hummingbirds? Bees? AND BUTTERFIES! ... along with for ourselves. .. oh sigh...

Kandis, you can't put the caterpillars somewhere else, unless it is on another host plant. They won't eat anything else except citrus, or native members of
the citrus family (Rutaceae), including northern pricklyash (Zanthoxylum americanum Mill.), Hercules-club (Zanthoxylum clava-herculis L.), lime pricklyash (Zanthoxylum fagara [L.] Sarg.), hoptree (Ptelea trifoliata L.), sea torchwood (Amyris elemifera L.), Mexican orange (Choisya dumosa [Torr.] A. Gray), and a variety of exotic Rutaceae including gasplant (Dictamnus albus L.) and white sapote (Casimiroa edulis Llave & Lex.). So, don't feel too badly. What you can do next time, is put them on a large and very mature citrus tree, that can spare some defoliation.

Patty S.