Horse Balm Bugs

Back in September, Noah asked me if I had any interest in some galls he’d found on horse balm (Collinsonia canadensis), a native woodland mint that looks like this:

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He described them as “like giant butterfly eggs,” and the photo he showed me was a good match for the illustration of Dasineura collinsoniae in Raymond J. Gagné’s Plant-feeding Gall Midges of North America.  According to the species account, “the single white larva in each gall breaks out to drop to the soil in early fall.  Larval characters place this species in the [supertribe] Oligotrophidi.  It is tentatively placed in Dasineura until adults are reared.”  

The fact that no one has apparently ever seen an adult of this species was as good a reason as any for us to get together for a wander in the woods, so a few days later we returned to the spot where he had found them.

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We gathered a decent number of the ones that seemed the most “ripe” (plump and easily detached from the plant), and I have these overwintering in a jar of soil in hopes of getting some adults in the spring.  While we were collecting the galls, we couldn’t help but notice that many of the leaves had been rolled, and in some cases nibbled at the midrib so that the portion with the roll drooped toward the ground.  Here’s an example with two rolls on a single leaf:

DSC_4453I usually try and steer clear of collecting leafrollers, but the caterpillars we found inside these rolls were so nice and spotty and distinctive-looking that I couldn’t resist taking a few of them home with me along with the galls.

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I checked the Database of the World’s Lepidopteran Hostplants, and the only caterpillar associates listed for Collinsonia were a few owlet moths (Noctuidae) and the Holly Blue (Celastrina argiolus), a lycaenid butterfly.  These larvae clearly weren’t any of those options; I was pretty sure they were some kind of pyraloid moth.  Searching BugGuide.Net for Collinsonia, I found this photo of a hermit sphinx (Lintneria eremitus) caterpillar feeding on the plant, and Terry Harrison’s comment here indicating that he has reared Pyrausta demantrialis (Crambidae) from this host in Illinois.  Since the latter is a pyraloid moth, this became my prime suspect.

Two weeks later, the caterpillars began to turn bright red, as many species do when done feeding and preparing to pupate.

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Some had already spun cocoons between the leaves and the Ziploc plastic bag in which I was keeping them…

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…but those that I got to in time were offered a loose wad of tissue paper in a fresh jar. Trying to raise caterpillars to adulthood in a plastic bag is a terrible idea because the moths will almost certainly mangle their wings when they emerge.

It being late in the season, I thought I might not get to see an adult (if at all) until next spring.  But in early November, these became my last moths to emerge in 2013.

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They clearly weren’t Pyrausta demantrialis, but browsing near this species on BugGuide, I quickly identified them as P. niveicilialis, which has been given the common name of “White-fringed Pyrausta Moth.”  I wasn’t able to find any previous host records for this species, but Terry informed me that he commonly finds the larvae feeding on leaves and flowers of Collinsonia in Illinois.

There are 63 North American species in the genus Pyrausta, and evidently a number of them are associated with mints (Lamiaceae).  Just browsing the common names on BugGuide, I see Mint-loving Pyrausta Moth (P. acrionalis), Southern Purple Mint Moth (P. laticlavia), and Orange Mint Moth (P. orphisalis).  This last one is the only other Pyrausta I’ve ever photographed, and that was nine years ago when I had just gotten my first digital camera.  Based on the HOSTS database, Orange Mint Moth caterpillars are only known to feed on Mentha species, the plants that even non-botanists know as mints, such as peppermint (Mentha X piperita).

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About Charley Eiseman

I am a freelance naturalist, endlessly fascinated by the interconnections of all the living and nonliving things around me. I am the lead author of Tracks & Sign of Insects and Other Invertebrates (Stackpole Books, 2010), and continue to collect photographs and information on this subject. These days I am especially drawn to galls, leaf mines, and other plant-insect interactions.
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5 Responses to Horse Balm Bugs

  1. Anonymous says:

    I know very little about “bugs” (mostly native orchids), but your blog entries always pique my interests. You have a wonderfully engaged way of writing — I can almost picture myself by your sde in your wanderings. Thanks for the information, and have a very Merry Christmas!

    Jim Fowler
    http://www.jfowlerphotography.com

  2. Sue Cloutier says:

    Another wonderful essay. A gift. Thank you and Happy Holidays!

  3. Charley — I read your posts not only because I love learning about the less-prominent inhabitants of my all-wildlife-welcome garden, but because you focus on the host plants as much as the insects, and learning about a new host plant that I can add to the naturalized areas of my garden is exciting! (Especially when they end up being natives in my state, like today’s plant Collinsonia canadensis) Thanks!

  4. Pingback: Leafminers Awaken! | BugTracks

  5. Pingback: Monthly Mystery #19: Aster Leaf Tubes | BugTracks

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