Although not common, they pack quite a wallop, so it's worth knowing what they are to avoid a painful sting. The saddleback caterpillar, also known as a slug caterpillar, is the larvae of a fairly non-descript moth. The caterpillar can get to about 1 inch long. It's mostly green, with brown on each end and a brown or purplish saddle-shaped marking in the middle of its back. These bristles, or spines, are mildly poisonous, and if you touch them, you will feel a painful sting.
Saddleback caterpillars feed on various plants.
However, because they are solitary and rather small, they don't do enough feeding to worry that they'll damage your garden plants. Another brightly colored insect that's best seen from a distance is known as a velvet ant or a cow-killer wasp. Resist the temptation to pick them up for a closer look, though. These are not ants, but wingless wasps. The female velvet ant drinks nectar from various flowers.