I found this on one of my tomato plants this afternoon, and later found one on some kale. I've never seen them before. They're about 1/4 inch long and look at first glance like bird poop. I think they're beetles because they definetly fly. When it first noticed I was there it plastered itself down flat to the leaf and didn't move, it really looked like bird poop then. I've been finding mysterious holes in all of my plant's leaves and I'm wondering, are these causing them. Thanks in advance for your help
If you have an image, you could attach it to the message you post for a better chance of getting an identification
Having said all that, I have managed to locate your beetle. It is a leaf beetle in the family Chrysomelidae and more particularly a tortoise beetle of the sub-family Cassidinae. Yours is known as the Clavate Tortoise Beetle (Plagiometriona clavata): http://bugguide.net/node/view/302620/bgimage
Quoting:Both adult and larval stages will eat leaves of various solanaceous plants, though their numbers are generally not high enough for their feeding to cause any significant damage. They feed on both the upper and undersides of leaves. Though they do fly, they are not easily disturbed.
, so they probably do make holes in the leaves of your tomato plants,