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Natural Perspectives: How not to be eaten

August 31, 2012|By Vic Leipzig and Lou Murray
(Courtesy Lou Murray )

Since taking up the hobby of mothing — photographing moths and other insects that are attracted to a black light at night — I've become more aware of daytime insects in our yard. Now that I'm looking for them, I'm seeing them everywhere.

One of the more spectacular species that I recently found in my yard was the milkweed bug. I confess that I had no idea what they were. I saw these black and orange beetle-like things crawling all over my bloodflower milkweeds in our butterfly garden. I had planted the milkweeds to attract monarch butterflies, and they've been doing a good job of that. I didn't know if I should try to get rid of those orange and black intruders or not. So I asked Vic, the resident biology instructor in the house.

Vic didn't recognize them either, so he sought an outside opinion. He took them to Larry Shaw of Orange County Vector Control District, who didn't even need to look at them. When he heard "big orange and black bugs on milkweed," he knew immediately that they were milkweed bugs. To humor Vic, Larry peered at the two bugs in a jar that Vic had brought to him. Yep, milkweed bugs.

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Turns out that unless you're a milkweed plant, they are pretty harmless. These bugs eat only milkweed seeds. By doing so, they ingest a toxin that milkweeds produce. They are immune to the toxin, but it makes them taste nasty to any bird that tries to eat them. A bird only needs to eat one of them to avoid the rest of them for life.

Milkweed bugs aren't the only insects that eat milkweed for self-protection. Vic says that everyone knows that Monarch butterflies and their caterpillars taste bad as well because of these toxins. I asked him if he would be willing to taste one to see how bad it really tastes. Husbands can give you the funniest looks sometimes.

The bright coloration of milkweed bugs and Monarch butterflies is a clue to birds not to eat those critters. Other insect species mimic this coloration to capitalize on that learned avoidance by birds. All an insect has to do is look like one that tastes bad, and it won't get eaten.

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