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Sunday, August 18, 2013

Milkweed Bugs, Large & Small

Last year I wrote a blog about the milkweed bug Oncopeltus fasciatus, which is also called the large milkweed bug. It's the kind I usually see on milkweed stems and leaves or sunning themselves on objects near milkweed. (Click here for that blog.)

Large milkweed bugs, Oncopeltus fasciatus, sunning on a fence rail. Adults sport a bright pattern of two black spots and a wide black band on an orange-red background. 
This week I stopped to look at the milkweed bug pictured below. It was sitting on milkweed flowers where its colors contrasted beautifully with the pink and cream blossoms. Looking more closely I saw by the pattern on its back that it was not the kind I usually see. It was the other milkweed bug: Lygaeus kalmii, also called the small milkweed bug.

A small milkweed bug, Lygaeus kalmii. The adult pattern is usually described as a red X on black, but I see a black heart and three red triangles on a red background. 
Like large milkweed bugs, small milkweed bugs also mainly eat milkweed seeds, piercing them with a sharp beak, injecting enzymes, and then sucking up the dissolved food. Both kinds of milkweed bugs also sometimes drink nectar from flowers -- the one above may have been having a sip when I spotted it.

8 comments:

  1. Nice photos of two very pretty bugs. Whenever I see a large stand of milkweed, I always check within to see what kind of fascinating insect life is happening there. There's another brightly colored bug that frequents milkweed exclusively, and that's the Red Milkweed Beetle (Tetraopes tetrophtalmus), which spends its entire life cycle on the plants. It's interesting that all these milkweed feeders (which absorb milkweed's toxins as they feed on them) advertise their own toxicity to predators by their bright red colors.

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    1. Thanks! A patch of milkweed is like a little universe: aphids, ladybugs, caterpillars, and everything. It is always worth stopping to explore. I'm still trying to get a good photo of red milkweed beetle -- hopefully to star in a future blog. Best, Julie

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  2. Julie - These are great photos and really show the difference. Do you ever see both on the same plant at the same time? Or do they partition the day/season/part of plant?

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    1. Thanks, Sue.

      I don't often see small milkweed bugs locally; the milkweeds plants are practically encrusted with large milkweeds bugs in all stages of development. I've read that smbs are less exclusive feeders on milkweed than lmbs and can develop on other plants -- maybe my little patch of milkweed is so crowded with lmbs and the others have moved out. :-)

      It could be coincidence, but I see smbs on flowers like in the photo. Best, J

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  3. i love these insects, if anyone wants to grow milkweed ,here is a source for seeds http://www.livemonarch.com/free-milkweed-seeds.htm

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  4. heres a clip i put together that shows both species for a bit, was looking amongst my files for the source material to put something longer together of milk bugs, not sure which library i put it in
    http://www.flickr.com/photos/13105441@N04/6230440107/in/set-72157606060570830

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