If galls, they are actually part of the leaf or stem, depending on what type of insect caused them. Use a magnifying glass, or microscope if you have one, to see if they are insects, egg clusters, galls, etc. Al

Those look like ticks to me. I would get on this right away, and if you have any pets, check them (and yourself!) thoroughly to make sure no ticks have attached themselves. You can use diatomaceous earth, which when sprinkled on them and in the areas they are crawling in, will pierce their exoskeletons and cause death from dehydration. Or if you want to go the non-organic route, look for a spray that kills ticks and spray it on any you see and around the general area. Any Home Depot or Lowe's or garden center will carry these items.

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

I found this online "But, while the adults rarely cause any problems, the young larvae will feed on the fine root hairs of your plants, causing them to lose vigor and develop yellow leaves. They can also tunnel into the base of cuttings or plant stems, which can be devastating for succulents, leeks, or onion seedlings in particular. Fungus gnats search out moist soil in which to lay their eggs. The eggs are about 1/100 inch in length and laid in clusters. Larvae are translucent gray to white worms, about 1/4 inch long, with shiny black heads. These insects can infest a crop from wet, algae-covered areas in the garden, from contaminated potting soil or by flying short distances from plant to plant." Fill a container with vinegar (red wine vinegar in my case) with a couple drops of dish soap added to break the surface tension. In a couple of hours there are around eight of them. I also ordered this on Amazon. I don´t want them all over my house when I get my meyer lemon tree inside. I hope this information helps.