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Fern Balls

fern ball 216At this time of year, many new sterile fern fronds have “fern balls” at their tips – something has taken the last few inches of the tip of the frond and stitched it together into a ball-shaped shelter bound with silk. If you open one of these balls, you may find frass – droppings from the immature insect that was dwelling within the ball while consuming the terminal leaflets of the fern. Sometimes, but not always, you’ll find the larva responsible for the frass. Many species of ferns, as well as other plants, are host to many species of larvae, and many of these larvae are immature moths. Pictured is Christmas Fern, Polystichum acrostichoides, which is likely the host of the larva of Herpetograma sphingealis, the Serpentine Webworm Moth, or its close relative, H. aeglealis. Larvae live in these shelters for about a month before pupating and emerging as small, brown moths.

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7 responses

  1. dellwvt

    Mary, as I read your posting this morning, I realize that I know very little about moths. What niche(s) do they fill in our ecosystems? How are they similar to butterflies, and how are they not? (Can you answer this in a few sentences!) Thanks! – Dell

    June 17, 2014 at 12:29 pm

    • Oh, dear, Dell. I’m afraid I don’t have time to go into moths, but if you have a copy of Naturally Curious and go to page 171, I put a chart in stating the major differences between moths and butterflies. I also think you’d find many of the answer to your questions in DISCOVERING MOTHS by John Himmelman.

      June 17, 2014 at 3:04 pm

      • dellwvt

        Thanks for the resources! I suspected there wouldn’t be a short answer!

        June 17, 2014 at 5:38 pm

  2. 0bovine

    Interesting. I had never heard the word “frass” until Sunday, and here it is again already! I first heard it in the context of the potential for using dogs to detect invasive insects like the Emerald Ash Borer.

    June 17, 2014 at 1:47 pm


    ALWAYS LOVE YOUR EMAILS!!!! LOOK FORWARD TO THEM! Are you able to tell me how to grow ferns? Are the stuff on the stems seeds to grow them from? We saw many VERY BEAUTIFUL AND TALL FERNS yesterday in Phillipston and would love to have them grow here in Lunenburg. Thank You! Dixie Paquin

    June 17, 2014 at 1:48 pm

    • Hi Dixie,
      A great book on ferns is Peterson’s Field Guide to Ferns: Northeastern and Central America (be sure to get the 2nd edition!). I have also heard good things about FERN GROWERS MANUAL by Barbara Joe Hoshizaki. Hope this helps! And yes, the spores that you find on ferns are what they grow from (similar to seeds) but they have two generations, so it’s a fairly long process, I believe.

      June 17, 2014 at 3:11 pm

    • Dixie – As it isn’t legal to dig any plants you find in the wild, you may be interested in these native plant nurseries in MA: I agree, ferns are awesome!

      June 18, 2014 at 2:00 pm

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