Plant-Insect Interaction: Milkweed tussock moth larvae feeding on a common milkweed

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Milkweed tussock moth caterpillars feeding on a common milkweed. Photographed 08/11/2013 near Palmyra, Michigan.

Yesterday afternoon I noticed a number of milkweed tussock moth larvae (Lepidoptera: ErebidaeEuchaetes egle) feeding on a common milkweed (Asclepias syriaca, Apocynaceae) near the edge of my yard. As with a number of other insects, these caterpillars have learned to overcome the chemical defenses milkweeds use to deter herbivory.

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Milkweed tussock moth caterpillars feeding on a common milkweed. Photographed 08/11/2013 near Palmyra, Michigan.

Milkweeds produce sticky white latex that tends to gum up the mouthparts of most insects. Milkweed tussock moth larvae get around this problem in two different ways. Smaller, younger larvae simply avoid the latex-bearing leaf veins, feeding instead on leaf tissue between the veins. This results in a “skeletonized” look to the leaves. Older larvae make incisions in the veins upstream from a given area, thereby cutting off the flow of latex to the spot where they want to eat.

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Milkweed tussock moth caterpillars feeding on a common milkweed. Photographed 08/11/2013 near Palmyra, Michigan.

Milkweeds also produce toxic cardiac glycosides that are harmful to most insects, but a few like these moths have developed a tolerance. Like some other insects they even incorporate it into their own tissues to make themselves toxic to predators. Although the defenses milkweeds have evolved to prevent herbivory by insects have helped them a great deal, some specialist insects have found an ideal niche feeding on these generally unpalatable plants.

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About Jeremy Sell

Science and nature nerd.
This entry was posted in Botany, Ecology, Entomology, Organism Interactions and tagged , , , . Bookmark the permalink.

5 Responses to Plant-Insect Interaction: Milkweed tussock moth larvae feeding on a common milkweed

  1. These are such cool caterpillars!

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  2. Jeremy Sell says:

    In spite of their apparent abundance, their striking coloration and wild tufts of hair do make them pretty cool to see.

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  3. I haven’t even seen these guys in my milkweed patch and no monarchs… Michelle

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  4. They look so soft and fluffy!

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  5. neihtn2012 says:

    Amazing larvae and cool photos! Thank you for the interesting information about them.

    Like

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