Two Different Poisonous Beetles

Here are a couple of beetles that are poisonous to eat, at least to birds and us mammals. I'm not sure they're poisonous enough to kill most birds, though it'll probably be sick for a while. [1]

They acquire their poisonous nature from eating milkweeds/dogbanes, 2 related and poisonous plants. But don't go tearing out any milkweeds/dogbanes from your yard; the plants are environmentally beneficial and are perfectly harmless if you don't swallow a bunch of it. [2] 

If you're going to ingest potentially dangerous chemicals to acquire a poisonous nature yourself, you want to advertise yourself as poisonous. Both these beetles advertise this visually, but they do it in different ways. The Red Milkweed Beetle has the more conventional advertisement; similar to Monarch butterflies and Large/Small Milkweed Bugs, their red coloring warns off at least some of their predators. The Dogbane Leaf Beetle is a bit more creative, and possibly even more eye-catching; their iridescent blue-green and metallic copper coloring probably gets them noticed too. 

Both these beetles will feed on both milkweeds and dogbanes, though their names suggest a preference. I've mostly seen Red Milkweed Beetles on milkweeds, and Dogbane Leaf Beetles on dogbanes.

July 31, 2021 at Duke Farms
Photo 149014215, (c) jpviolette, some rights reserved (CC BY-NC)

July 31, 2021 at Duke Farms
Photo 149014424, (c) jpviolette, some rights reserved (CC BY-NC)

[1] I think arthropods like mantises and spiders can still eat them more or less safely.

[2] I have heard of people who eat milkweed, though the process involves boiling them in water, tossing the water out, boiling them in more water, tossing that water out, and after a few iterations of this you've probably removed the poisonous substances (like cardiac glycosides) from them. It sounds like a lot of work just to say you've eaten milkweed without getting sick.