white powder on antheraea sp. cocoons

    Hello all,


    This has me bugging for years now. Does anyone know what the white powdery substance is that can be found on anthereae cocoons?

    Well, "on" might not be the correct word, it's more like "in", like trapped between the layers of silk and it falls out when you pull the layers of silk apart.

    Does anyone know what it is and what it's function is?


    I also noticed that the few individuals that pupate without spinning a cocoon are covered in that same white stuff when they are close to becoming a prepupa.


    Please enlighten me! :smiling_face:


    Anna

    • We specialise in rare and common butterflies from the Neotropical (Central/South America, Caribbean Islands) and Holarctic regions (North America, Europe, Asia).
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    I too have seen this with some Samia cocoons , Lackey moth and Lappet cocoons . Lackey especially are covered in a yellow powder and lots of it .

    I wonder if it's foul tasting to predators so they learn to leave them alone or the powder is irritating to their eyes . Another possibility is that it could be some kind of anti fungal powder . These are only ideas/thoughts with no proof behind them .

    oh yeah now that you mention Samia, i didn't notice anything with their cocoons, but the caterpillars themselves have this kind of white waxy substance all over their body, when you rub your fingers together after handling the Samia caterpillars it feels yucky and weird and waxy. I thought it might be some moisture regulating thing, or yeah, just something that tastes bad for predators.


    The powder in the anthraea cocoons make me sneeze.

    I can’t be specific for Antherea but most Saturniid and other families‘ cocoon builders impregnate their cocoons during spinning several times with a liquid comprised at least partly of - I think it was - oxalate crystals. This gives the cocoon additional strengths by „melting“ the silken strands together and this hardening the cocoon.


    I made impressive video footage with my GoPro of a Saturnia pyri caterpillar spinning the cocoon and adding several drops of this liquid. Upon fast forward one could see that the cocoon shrunk a considerable bit. After that, the caterpillar widened it again by stretching the body, followed by another drop of liquid.


    Another effect is that this liquid turns the actually white silk dark. This might, however, only be an effect of moisture, not of the oxalate. You can strengthen this effect by spraying the fresh cocoon with pure water.


    The waxy powder of Samia and Attacus (and many more) species has nothing to do with that.

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