Down the Rabbit Hole

I’ve managed to study insects intensively for over a decade, writing two books and publishing over 50 scientific papers that included the descriptions of 76 new species and one new genus, without ever learning to dissect anything. I have relied on various collaborators to do the dirty work of examining genitalia and other minutia necessary for many identifications and all species descriptions, leaving me free to focus on rearing and documenting natural history. But as boxes of undescribed and undetermined moth species have continued to pile up in my office with no progress toward getting names put on them, I’ve become resigned to the fact that it’s up to me to ensure that all of these wee mothies have not died in vain.

A few years ago Jason Dombroskie was kind enough to give me and Julia a lesson in dissecting micro-moths, but the laundry list of chemicals, other supplies, and equipment required to practice it at home created an inertia that has been hard to overcome, especially when our time is already more than full of things that we don’t need to acquire new skills or materials to do. Last month we finally bit the bullet and got set up to do it, which included studying this tutorial prepared by Sangmi Lee and Richard Brown, and getting additional advice from Terry Harrison and Tony Thomas.

Beginning two weeks ago, we practiced on a few specimens I had collected 15+ years ago for the one entomology class I ever took (a general undergraduate course I took while in grad school at the University of Vermont; the specimens were rendered useless when the professor told the TA to throw out all the students’ notebooks, which contained the collection data, before we had a chance to pick them up at the end of the semester, so nothing was at stake if Julia and I botched the dissections), and that went well enough that two days ago I decided to try out dissecting some undetermined specimens I had reared, and see if I could use the genitalia to identify them.

I started with a relatively large one, because while the method is basically the same for all moths, it gets more difficult the smaller you go, and I don’t want to risk ruining any precious tiny leafminer specimens, which is what I’ve mostly got. Back in late July of 2017, during one of our visits to Nantucket to search for leafminers and other understudied herbivorous insects, Kelly Omand led me and Julia to a little patch of dwarf prairie willow (Salicaceae: Salix occidentalis) to see if there were any unusual bugs on this uncommon plant. We didn’t see any galls or leaf mines, but some kind of moth larvae had tied some of the leaves together in little clumps.

We collected a few of these clumps, and in October this moth emerged:

With a wingspan of around 2 cm, this was many times larger than the moths I know anything about, but I knew it was something in the superfamily Pyraloidea and figured it was probably in the family Crambidae. I posted this photo on good old, where Aaron Hunt and Kyhl Austin confirmed my suspicion and placed it in the subfamily Pyraustinae, and it has been sitting there ever since. With a moth this nondescript, photos just aren’t going to cut it if you’re looking for a species- or even genus-level ID.

Fortunately, I saved the specimen—which involved relatively humanely gassing it to death in a jar with ammonium carbonate, after which Julia pinned it, spread its wings, and mounted it; and then keeping it safe from marauding booklice, dermestid beetles, and the like for the next several years by periodically refreshing the mothballs in its airtight box. To get a look at the genitalia, I had to carefully remove the abdomen with forceps (some specimens would much rather break in the middle of the thorax, so that the hindwings come off along with the abdomen), then place it in a vial of ~20% potassium hydroxide overnight (Terry advised that first dunking it in 90% alcohol helps it sink in the KOH instead of floating up at the top) to dissolve some of the extraneous tissue. In the morning I moved the abdomen into a tiny puddle of 30% ethanol where I used fine-tipped paintbrushes to remove scales from the surface, then moved it into a tiny puddle of a red stain called “Eosin Y” where I let it sit for a few hours. Next I rinsed it in another tiny puddle of alcohol and then moved it into a tiny puddle of another stain called “Chlorazol Black,” where I left in for another hour or so.

Now (after rinsing the abdomen in another tiny puddle of ethanol) it was time to actually do the dissection, which involves a pair of super fine-tipped foreceps in each hand. Normally with males you’re supposed to keep the “pelt” of the abdomen intact and just remove the genitalia from the tip, whereas with females you carefully tear (or snip, if you have a pair of $300 tiny scissors) the abdomen open along one side, because females have more complicated internal parts to deal with. This specimen had appeared to be a male, because the frenulum consisted of a single bristle, but in my previous practice session I had dissected several pyraloid moths with that same feature and all had turned out to be females. So I didn’t trust that determination and I opened up the “pelt” just to be sure there wasn’t a corpus bursa, and so forth, in there.

There wasn’t, but the tip of the abdomen also didn’t look very much like that of any male moth I had seen previously, so I puzzled over this for a bit until I finally decided to pull off a thin membrane that seemed to be enclosing it, and voila! The valvae magically fell open and it was most definitely a male. I don’t yet have a good setup for taking photos through a microscope (which will require, among other things, a better microscope), but here’s what it looked like:

The thing poking out at lower right is what most lepidopterists call the “aedeagus,” but Jason and Kyhl say that’s technically wrong (I forget why) and use “phallus” instead, which certainly makes it clearer to non-entomologists what we’re talking about. The phallus sort of gets in the way of things and you’re generally supposed to remove it, so I did, and then I moved both parts into a drop of lactic acid I’d placed on a microscope slide, and then flattened it all out with a coverslip, which always results in a few bubbles, but trying to fix those only creates lots more bubbles, so I left them as they were:

So now what? Now it was time to consult the compendium of North American pyraustine moths and figure out who this moth was. Fortunately, such a compendium exists (it does not exist for Gracillariidae, the largest family of leaf-mining moths, but we’ll come to that problem later), and the PDF can be downloaded for free here if you want to play along: Munroe (1976), the one labeled “Fascicle 13.2A: Pyralidae, Pyraustinae (part 1).”

Turn to page 8 and we find that what is now Crambidae: subfamily Pyraustinae was treated as Pyralidae: Pyraustinae: tribe Pyraustini in 1976, and on the next page we find that the key to genera of Pyraustini is based entirely on genitalia. After a few couplets it is based entirely on male genitalia, so it’s a good thing that’s what we’ve got! Soon flustered by all the unfamiliar terminology, and irritated by the complete lack of references to any figures, we take to flipping through all the photos of genitalia in the back of the book, and we find that this clearly isn’t any of the species illustrated. So then we return to the key and start trying to figure out what all the terms mean, one by one.

I labeled the photo with my interpretations of all of the terms that came up in the key (based on various online sources, including the glossary at Pacific Northwest Moths and several highly pixilated thumbnail images from that came up in a Google image search—I can’t see the full versions because my malware-blocking software won’t let me visit that website), and then added five more (lower right) for completeness. I welcome corrections if any lepidopterists are reading this!

The genus I landed on was Loxostege, and I didn’t try the species key because a quick look at photos of Loxostege adults suggested that this isn’t the right genus. And that’s where I’ll leave this story for now, because I don’t know where to go from here without some input from someone who knows more about this than I do.

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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15 Responses to Down the Rabbit Hole

  1. Steph Eastwood says:

    Delighted to see your success learning these new skills, Charley. You are inspiring, and this was fun to read.

  2. irisclearwater says:

    Thank you so much for sharing the journey with so much detail, and congratulations on leaving the inertia and taking on the challenge! I’m so glad you have such a wonderful partner in Julia to the share it with you.

    I can so relate, as I’ve had similar experiences often when trying to key out plants. It makes me feel better to know it’s just the way of the process.

    I hope that you find the guides to help you feel more confident with this process, though I imagine you may come to several dead ends like this, as there are many species that you are first describing. What to do when this inevitably happens?

  3. ophis says:

    Am wondering how many new sp. of genus Homo I could describe if I started looking at fine details of genitalia (male only of course). But my critics would say I neglected to demonstrate that they are reproductively isolated…

  4. Anonymous says:


  5. John Snell says:

    A wonderful piece of work. Thank you for sharing it, frustrations and all.

  6. lfelliott says:

    Inspiring as always. Inspiring enough to try it myself? We’ll see. It will be on my list along with mosses, probably after mosses. Wonderful that you weren’t successful and excellent that you wrote it up anyway. A real life story.

  7. Tanya Dapkey says:

    I’m working on a revision of Hahncappsia of Costa Rica. I also did some genitalia dissections. Would love to touch base to see if I can connect you to the right people and/or collaborate. I need motivation to finish my manuscript. If you are interested, my email is

  8. hcethatsme says:

    Thanks so much for writing in delightful detail so we can peek down the rabbit hole vicariously. Good luck with the piles of moths – it will be cool to find out how many new species lurk in there!

  9. Nancy Lowe says:

    Very cool post! Charley, I don’t know if you remember, but we met years ago in Nantucket at a Nantucket biodiversity conference. I was working with John Pickering, and also I’m friends with Sarah Oktay (through OBFS networks).

    I recently relocated to Northampton, MA and I love living in New England.

    I have a Nikon AZ-100 scope which is unusual in that it has capacity to go from 8x to 320x. It’s set up with imaging software but I haven’t finished calibrating it for measurements yet (which can be superimposed on the image). Let me know if you’re ever interested in coming down to use it sometime. -Nancy

    • Good to hear from you Nancy, and thanks for the offer! I’m working on acquiring a better scope, but I may well be in touch if I end up with good slides of something interesting before that happens.

  10. Pingback: Through the Looking-Glass | BugTracks

  11. Ying Luo says:

    I love reading about genitalia dissection adventures..! Yours look great.

    Soon I will have to start dissecting the gracillariids and I have no idea where to start (I suspect working on such tiny things will require a whole other skill set). Luckily someone has offered to show me how they do it, phew.

  12. Anonymous says:

    I’ve been wondering how they do those dissections and a purely scientific explanation would have left met behind after two sentences. So many thanks for a very a delightful read! 😊

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