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Broad-leaved Helleborine Dispersing Pollen

8-10-16  helleborine pollinia 021Having known since childhood that most insects have only one pair of antennae, imagine my surprise when I came upon a hornet on Queen Anne’s Lace that appeared to have two:  a pair of slender, black antennae, and between them, a shorter pair of white ones.  A bit of research revealed to me that in fact, these white “antennae” were actually the pollen sacs (pollinia) of an introduced and somewhat invasive orchid, Broad-leaved Helleborine (Epipactis helleborine).

Broad-leaved Helleborine is entirely dependent on insects to spread its pollen, especially wasps.  It attracts them with nectar, which is said to have an alcoholic and narcotic effect which may help with the spreading of pollen, as an inebriated wasp is less likely to clean pollen off its body before leaving.   Helleborine also produces a chemical which other plants produce and use to signal that they are being attacked by insects. It is used purely as a ruse by Helleborine, in order to attract wasps, Helleborine’s primary pollinators, who arrive to fend off other insects, and end up inadvertently collecting Helleborine’s pollinia.

Unlike the pollen of most plants,  Helleborine’s pollen grains are so sticky that they cannot separate – thus, the entire package of pollen remains intact and is removed at one time.  Wasps are capable of reaching the plant’s nectar without disturbing the pollinia, but cannot crawl out of the flower without striking against and detaching them and in so doing,  getting them stuck to their heads.    Can you find the pollinia in the insert photograph of a Broad-leaved Helleborine flower (which has not been visited by a wasp yet)?

Due to computer issues, Naturally Curious will resume posts next Tuesday, August 16.

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6 responses

  1. Spry

    When you say the wasps ‘fend off’ other insects, do you mean they come to eat them, as prey, or to protect the nectar source?

    August 10, 2016 at 7:56 am

    • Mainly to protect the nectar source, but they also do prey on insects that they feed to their larvae.

      August 10, 2016 at 9:13 am

  2. K

    Thanks for posting this – have been trying to id this orchid. Now it makes sense that it “disappeared “when I went back to see it again. Probably eaten by something that likes the effect it produces.

    August 10, 2016 at 8:00 am

  3. Wallie Hammer

    Hi Mary, I am reading an interesting book called: The New Wild, by Fred Pearce- subtitle, ‘why invasive species will be natures salvation’- he is basically claiming there are no native species!
    As a life long naturalist I must say it is spinning my head around- I’d love your take on it-

    August 10, 2016 at 10:37 am

    • Hi Wally, I need to read this book, but it may be a while before I can fit it in! Thanks for telling me about it. New concept to me.

      August 15, 2016 at 2:04 pm

  4. Your posts are so informative, Mary. I’m always learning new and interesting tidbits! 🙂

    August 10, 2016 at 12:11 pm

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