Swamp Milkweed Leaf Beetle Larva

Subject: gray and black beetle-like bug on swamp milkweed
Location: Fenton, MO
September 4, 2016 1:51 pm
Dear Bugman,
I ran into this creature while inspecting my swamp milkweed for monarch caterpillars. I found ver 10 caterpillars as well as this gray and sort of shiny creature. It has 5 black dots on each side and I think I see 6 legs but really small. its about the size of a ladybug. Found it on underside of Swamp. Milkweed leaf toward top of stem. I cannot tell where to begin to find out what this little guy or gal is and if he/she means harm to my milkweed or my monarch caterpillars.
Thanks so much!
Signature: fran

Swamp Milkweed Beetle Larva
Swamp Milkweed Leaf Beetle Larva

Dear Fran,
This is the larva of a Swamp Milkweed Leaf Beetle,
Labidomera clivicollis, and we identified it on BugGuide based on this image.  According to BugGuide:  “Larvae and adults cut several side-veins of a milkweed leaf prior to feeding, to reduce the sticky latex that would otherwise be produced at their feeding sites.”  So, the larvae and adults of the Swamp Milkweed Leaf Beetle share the same food source as the Monarch Butterfly, and unless the beetles are so populous that they defoliate the plants, they are not a threat to either the milkweed or the Monarch caterpillars.

Thanks you so much.  A few folks had thought it might be a false Potato Bug larvae??? Since I found it on a swamp milkweed leaf, a Swamp Milkweed Leaf Beetle makes sense!
Thanks do much!


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