On June 9, I was exploring a powerline corridor in Kent, New York when I spotted some little jewels that I recognized as the poop-covered eggs of a leaf beetle in the tribe Clytrini (Chrysomelidae: Crytocephalinae). They were the first I had seen since July 2008, when I photographed the ones in Arizona that are shown on page 165 of Tracks & Sign of Insects and Other Invertebrates. I am now much better set up for macro photography than I was when I wrote that book, but lately I have taken to only bringing my phone with me to take photos while conducting fieldwork, instead of stumbling around with two DSLRs dangling from my neck, so I collected one of the egg clusters to photograph later.
I figured I might as well hang onto them to see if they hatched, and on June 21 I was treated to the sight of tiny beetle larvae hauling around their egg coverings as portable houses.
Some case-bearing leaf beetles (Cryptocephalinae) feed on living leaves, in which case the identity of the plant their eggs are found on may be significant, but as I wrote of the Clytrini on page 254, larvae of at least some species feed on debris in ant nests. The egg cluster I collected was on some kind of grass, but I saw a few others on other plants in the same area, so I assumed these were a debris-feeding species. I put some miscellaneous living and dead plant material and soil/duff in the vial with them, but I did not succeed in rearing them further. For what it’s worth, here are the two species of Clytrini I’ve met as adults:
Anomoea laticlavia (this one was in Minnesota, and I found another one in Massachusetts)…
The vast majority of leafminers are highly host-specific, feeding in leaves of a single plant genus or a few closely related genera. For this reason, it has always bothered me that the weevil Orchestes mixtus (Curculionidae) mines leaves of every genus in the birch family (Betulaceae: Alnus, Betula, Carpinus, Corylus, Ostrya; otherwise known as alder, birch, musclewood, hazelnut, and hophornbeam), plus elm (Ulmaceae: Ulmus), which is not only in a different family but even a different order (Rosales instead of Fagales).
Meanwhile, another species that is basically identical except for its genitalia, Orchestes pallicornis, feeds on a bunch of different genera in the rose family (Rosaceae: Amelanchier, Aronia, Crataegus, Cydonia, Malus, Mespilus, Prunus, Sorbus; otherwise known as shadbush, chokeberry, hawthorn, quince, apple, medlar, cherry/plum/peach, and mountain-ash), which belongs to the same order as elm.
Wouldn’t it make more sense for the species on elm to be O. pallicornis, or maybe a third species? As I noted in a paper about assorted weevils a couple of years ago*, O. mixtus is abundant on plants in the birch family in New England, but conspicuously absent on elms here. All the records of it feeding on elm are from farther south and/or west: Ontario, Virginia, West Virginia, Oklahoma, Arkansas, and Texas. Highly suspicious.
In the spring of 2023, Tracy Feldman found O. mixtus mining a leaf of winged elm (Ulmusalata) in North Carolina. I seized on the opportunity to do a little DNA comparison; I collected some Orchestes mines on black birch (Betula lenta) and pin cherry (Prunus pensylvanica) and reared adults of O. mixtus and O. pallicornis from them, respectively. I sent them off to Matt Bertone, along with Tracy’s adult reared from elm, and Matt and his colleague Swarnalatha Moparthi performed the magic technique known as “DNA barcoding,” which somehow takes a tiny chunk of tissue from an organism and translates it into a long string of C’s and G’s and T’s and A’s on a computer. This string of letters (the “barcode”) is comparable from one sample to the next because it begins at the same point on the same gene. The barcode is just a little snippet of one gene, and not the whole genome, which would be ideal for reaching a definite conclusion but is much more expensive to obtain. In general, it is assumed that two barcodes that differ by less than one percent represent the same species, and those that differ by more than a few percent represent different species; in between is a bit of a gray area. Humans and chimpanzees differ by 1.2% (I believe that’s based on the whole genome).
As reported in our short paper that was published this spring**, the barcode of the specimen from elm (whose barcode can be seen here) did not differ notably from the barcode of the birch specimen; they both correspond with the barcode identification number (BIN) BOLD:AAM7599. Specimens with the same BIN are assumed to represent the same species in the absence of evidence to the contrary. In this case, no differences have been found in the adult weevils (including genitalia), so the only evidence to the contrary is the limited geographic distribution of elm-feeding O. mixtus.
The specimen from pin cherry, on the other hand, differed by 8.7–10.7% from other specimens of O. pallicornis! So we seem to have found a cryptic species we weren’t looking for. None of us being weevil taxonomists, we’ve left it to others to decide what to do about that. Checking our barcode against the whole Barcode of Life Database (BOLD) just now, I find that the most similar barcode (which is also from a specimen identified as O. pallicornis) is a bit closer than the range we reported, differing by 7.95%, but this is still a huge difference for something that is supposed to be the same species. Foreshadowing this result (in hindsight), in my 2022 weevil paper I noted that three O. pallicornis adults I reared from black cherry (Prunus serotina) showed no interest in a shadbush (Amelanchier) leaf I offered them, but immediately began to feed on a black cherry leaf that I later added to the rearing vial.
Several years ago, Björn Rulik (who was a coauthor on both of my papers describing new species of leaf-mining dark-winged fungus gnats) was kind enough to barcode 100 or so specimens I sent him belonging to another group of leaf-mining beetles, the hispines (Chrysomelidae: Cassidinae: Chalepini). The results were reported in a paper that was published a few days ago***. The main focus of this paper was presenting new natural history information (and reviewing what was previously known) about a bunch of different species, but the barcoding results echoed what I just described for the weevil barcoding paper, so I’ll highlight those here.
I had three species that I wondered about being complexes of cryptic species based on what I knew of the hosts and habits of the larvae. The first species, shown in figures 128 and 129 below, is Baliosus nervosus, which has the common name “basswood leafminer,” but in addition to basswood (Malvaceae: Tilia americana), it feeds on elms, plus members of the birch and rose families, plus members of the beech family (Fagaceae: Castanea, Quercus; = chestnut and oak). A single beetle species, or one or more host-specific species that look similar?
It turned out that specimens reared from apple, alder, chestnut, oak, and basswood all had the same DNA barcode, but then there were some specimens from basswood (including the one in Figure 129) that differed from everything else by more than 10%! Evidently another cryptic species, but again not exactly the result I was looking for.
My next target species was Sumitrosis inaequalis, which feeds on many different genera in the aster family (Asteraceae). I had noticed that its mines on asters in the genus Symphyotrichum virtually always look like the one on the left below—long and narrow, with frass deposited along the sides—whereas mines on every other host genus virtually always look like the one on the right: a compact blotch with crisscrossing frass threads deposited throughout, except at the edges. Do these two patterns represent two different beetle species?
Nope, the barcodes from these two different types were all jumbled together. Sumitrosis inaequalis is the beetle in Figure 151 below.
The third species I wanted to investigate is another Sumitrosis, S. rosea. This species mines leaves of a variety of legumes (Fabaceae), plus wood nettle (Urticaceae: Laportea) and bittersweet (Celastraceae: Celastrus). I’m not the only one to suggest that these disparate hosts may correspond with different beetle species. Figure 153 above is a typical (pale brown) legume-associated adult, and the black one in Fig. 156 was reared from bittersweet. Surely these are two different species, right? Well, if so, they’re not as easy to distinguish as you might think, because Figures 154 and 155 show two adults that are probably siblings; they were reared from the same collection of wood nettle leaves. And once again, the barcodes of adults reared from these three different host families were all mixed up together, so these seem to all represent a single variable species with peculiar tastes.
But then, in our random barcoding of other hispines, which was just done to get a sense of the typical variation in barcodes within and between species, we turned up one Sumitrosis result that seems to represent the sort of thing I was looking for. Sumitrosis ancoroides is known to feed on two different legume genera, Strophostyles and Stylosanthes. The specimens that Tracy Feldman reared from Stylosanthes biflora (pencil flower) in North Carolina (Figure 149) differed by 10.72% from the ones that Mike Palmer reared from Strophostyles helvola (trailing fuzzybean) in Oklahoma (Figure 150). There do seem to be some differences between these two adult beetles; I’m hoping someone else will investigate this and figure out if these are consistent differences that can be used to describe a new species. Differing barcodes also suggest that some other species, such as Microrhopala excavata and Odontota horni, warrant a closer look, although I must say I’m less excited about cryptic species that don’t seem to correspond with any obvious differences in host plants or larval biology.
* Eiseman, Charles S. 2022. New rearing records and observations of weevils with folivorous larvae (Coleoptera: Curculionidae). Proceedings of the Entomological Society of Washington 123(4): 727–740.
** Eiseman, Charles S., Tracy S. Feldman, Swarnalatha Moparthi, and Matthew A. Bertone. 2024. Investigation of possible cryptic species within Orchestes mixtus Blatchley and O. pallicornis Say (Coleoptera: Curculionidae: Curculioninae: Rhamphini) using DNA barcoding. Proceedings of the Entomological Society of Washington 126(2): 243–246.
*** Eiseman, Charles S., Tracy S. Feldman, and Michael W. Palmer. 2024. New larval host records, parasitoid records, and DNA barcoding data for North American leaf-mining leaf beetles (Coleoptera: Chrysomeloidea). Zootaxa 5549(1): 1–60.
Things have been pretty quiet around here on the BugTracks blog lately, but I think that’s going to change pretty soon. As usual, I was busy with fieldwork from May to October, and for the past few weeks I’ve been busy writing, revising, and reviewing a bunch of papers (as well as putting together the monthly installment of the third edition of Leafminers of North America), but any day now I’m going to start going through all my photos from this year, and when I come across anything particularly interesting, I’ll write about it here.
In the meantime, as with every year in recent memory, I’ve just put together a wall calendar as a thank-you gift for my most generous patrons, and I will also send a copy to anyone who makes a donation of at least $30 (the amount WordPress charges me each year to keep this blog free of annoying ads) before the end of November, which you can do here (select “Send,” and then include your mailing address in the notes). In this year’s calendar, each month features a (more or less seasonally appropriate) leaf mine that is either a total mystery or needs further investigation (e.g., I’ve reared some adult females of the insect responsible for the mine, but males are needed to identify the species, or describe it if it turns out to be new).
And speaking of beetles associated with galls (which we were, briefly, several weeks ago in my previous post), here’s an odd thing I noticed last May while wandering in the woods of Aton Forest in northwestern Connecticut. A lot of the leaves of shagbark hickories (Juglandaceae: Carya ovata) were covered with little round, flattened galls:
Nothing too odd about that; galls like these are a common sight on hickories, and they are caused by aphidlike insects called phylloxerans (Phylloxeridae: Phylloxera spp.). Here’s a larger (7 mm across) gall of a different species that I cut open 14 years ago to get a look at the Phylloxera nymphs within:
The odd thing was that I kept seeing little weevils on the leaves with the galls. I didn’t think much of the first one I saw, but after the second or third weevil, I started to wonder, “What is it with you guys and these galls?” As I wondered this, I had a vague recollection of having seen weevil larvae come out of phylloxera galls at some point. And I wondered if the dark blemishes I kept seeing on these galls had been caused by the weevils I was seeing, maybe chewing holes in which to lay eggs. The one weevil I photographed in the field was certainly doing something to one of the galls:
So naturally, after I ate the sandwich I had brought, I put several gall-laden leaves in my sandwich box along with a few weevils, including a mating pair. At home I got some better photos of the weevils, including this one:
And when trying to get better photos of the galls, it was hard to find any that didn’t have the dark blemishes on them—they were made from the lower surface but the damage was often visible from the upper surface as well.
On May 29, twelve days after I had collected the galls, a couple of squirming, legless weevil larvae appeared in my sandwich box.
The galls, to my surprise, had continued to develop on the detached leaves, and were now nearly spherical in some cases.
Some galls had been visibly munched, presumably by the weevil larvae, although in some cases this may have been from a few caterpillars that had hatched on the collected leaves and were now devouring them.
One of the caterpillars was this little inchworm, which I first noticed on May 19:
By May 27 it looked like this, and was recognizable as the larva of a “half-wing” (Geometridae: Phigalia titea):
There were also a couple of owlet moth caterpillars, which looked like this on May 27:
By May 29 the second one had molted, confirming my suspicion that these were larvae of the “ruby quaker” (Noctuidae: Orthosia rubescens):
Anyway, I moved the weevil larvae to a jar with soil in the bottom for the larvae to burrow into. On June 11, two adult weevils appeared in the jar. One looked much like the ones I’d photographed previously…
…and one was plain black, without the red markings on the elytra.
Knowing what these weevils did for a living, it took only a quick internet search to identify them as Anthonomus suturalis (Curculionidae), which has been a known associate of phylloxera galls since 1866. The account by Gates & Burke (1972)* makes it sound like the munching on the last gall shown above was in fact caused by the caterpillars rather than the weevil larvae: “By the time a larva has completed its development, the tissue of the inner wall of the gall has been consumed. There is no tunneling by the larvae as in cases of some other Anthonomus inquilines; instead, the inner tissue of the galls is rather smoothly gnawed away. The frass resulting from the activities of a larva is packed in one end of the gall.”
It’s just as well that I didn’t discover anything new about these weevils, because evidently no one is willing to review my papers about weevils anymore. I submitted a two-page manuscript on leaf-mining weevils to a journal a full year ago, and another one-page manuscript half a year ago, and I’m still waiting for reviews on both of these. This makes me a bit grumpy since I’ve never taken more than a few weeks to review a manuscript, and I only take that long if the paper is several hundred pages long.
As for my vague recollection of having seen weevil larvae come out of phylloxera galls before, I checked my files, and what I was remembering was actually a single gall on a shagbark hickory catkin that I found on the ground on June 1, 2018, possibly having been nipped off by a squirrel. I didn’t take a picture of the gall until eight days later, when things had started emerging from it; at this point the plant material had all turned brown, but you can still get a general idea of what it looked like:
Two identical weevil larvae emerged from this gall, one on June 5 and one on June 9. They were identical with one another, but looked nothing like the larvae of Anthonomus suturalis pictured above.
Also on June 9, this fly larva appeared in the jar with the gall, apparently having emerged from it along with the weevil larvae. I assume it is one of the hover flies (Syrphidae) that are predators of aphids and other insects.
I put these three larvae, along with the gall, in a jar of soil with the hope of rearing adults, but all that ever emerged—in March of the following year—was this blastobasid moth, which Aaron Hunt identified as Asaphocrita busckiella (which he believes to be a species complex):
I’m not sure if anything is known about the larvae of A. busckiella, but I see that A. aphidiella was reported in 1886 to have been “reared from the larvae feeding on the contents of Phylloxera hickory galls.” Blastobasids are known as “scavenger moths”, and I presume the larva was feeding on the damaged plant tissue and maybe on the weevil larvae’s frass rather than preying on whatever phylloxerans weren’t eaten by the fly larva. As for what kind of weevil the weevil larvae belonged to, I have no idea!
* Gates, Danny B. and Horace R. Burke. 1972. Review of the gall-inhabiting weevils of the genus Anthonomus, with description and biology of a new species (Coleoptera: Curculionidae). Annals of the Entomological Society of America 65(5): 1215-1224.
Normally I limit my investigations of stem-feeding insects to those that produce some kind of external evidence that catches my eye (a certain wingstem stem being an exception), but last spring , for whatever reason, I decided to have a peek inside a dead stem of tall blue lettuce (Asteraceae: Lactuca biennis) that had been leaning against the side of my house, right by the front door, all winter long. On April 12, I broke off a short chunk from the top of the stem, split it lengthwise, and immediately saw that there were little round cells in the walls of the stem with larvae inside.
I guessed these must be cryptic wasp galls—something I’d first become aware of in 2019 when two adults of Aulacidea harringtoni (Cynipidae) emerged from a two-inch piece of a Lactuca canadensis stem I’d collected the previous July because it had a puparium of a stem-mining agromyzid fly on the surface.
I put the split pieces of the L. biennis stem in a jar, along with a couple of intact pieces from farther down the stem, and put the jar on a shelf in my office to find out if my guess was right.
Between May 9 and June 10, ten of these wasps emerged in the jar:
These are eurytomid wasps (Eurytoma sp.), which are parasitoids of gall insects rather than being gall inducers themselves. When the first ones emerged, I figured this would be a good time to see some wasp pupae, so I split one of the intact stem pieces. The exposed cells still had larvae inside, and there was also a spider living in the stem’s hollow center.
I think this spider is in the genus Euryopis (Theridiidae), which makes distinctive tufted egg sacs—one of which (maybe) is shown in this post. Here’s a closer view of the above wasp larva:
On May 27, this beetle appeared in the jar.
This is Isohydnocera curtipennis (Cleridae), which I had seen a couple of times in June 2020 wandering around on milkweed plants in my yard. Until this one appeared in that jar, I had been completely unaware that these beetles develop in galls of other insects. It turns out this same species has been reared from stem galls of the goldenrod gall moth Gnorimoschema gallaesolidaginis (Gelechiidae), and of Euura salicisnodus (Tenthredinidae), a sawfly that causes galls in willow stems*.
Between May 29 and June 27, 22 gall wasp adults emerged. Louis Nastasi tells me they belong to an undescribed species of Aulacidea.
I did eventually see a gall wasp pupa, on June 10. I think it was from one of the larvae whose cells I had broken open, and was found loose on the bottom of the jar.
Meanwhile, another 24 parasitoid wasps emerged between June 18 and 27. Twenty-two of them were pteromalids; I’m not sure if the ones shown below are two different species or differently colored male and female of the same species. Probably I’ll never know; I’ve never been able to get anyone to identify the pteromalids I’ve reared over the years.
And there were two of these ormyrids (Ormyrus sp.).
I got the feeling that more and more wasps would just keep emerging indefinitely, but I had to leave for a six-week road trip at the beginning of July, so that’s where the story ends. If you want to learn more about these herb gall wasps—and maybe help make some new discoveries—take a look at Louis Nastasi’s post here. (Most of the galls, by the way, are externally obvious, not cryptic like the ones in this lettuce stem.)
[Edit, 3/20/2024: Louis saw this post and he assures me that all of these parasitoid wasps are undescribed, not just the Aulacidea, for which he already has a name picked out, and he thinks the pteromalids may belong to the genus Homoporus.]
* Sabrosky, Curtis W. 1934. Notes on the larva and larval habit of Isohydnocera curtipennis (Newmn.) (Coleoptera, Cleridae). Journal of the Kansas Entomological Society 7(2): 65-68.
Uh-oh, spring has arrived—as evidenced by the hazelnuts starting to bloom in my yard—and I haven’t finished going through last year’s photos yet. I have, however, made it far enough to finish this post I started a few months ago. The story starts in August 2020 when, as you may recall, I was keeping a running list of all the leafminers I found in my yard. The 23rd installment of that series included this entry toward the bottom:
“I don’t remember specifically planting garden phlox (Polemoniaceae: Phlox paniculata), but it’s been jumping around our yard for a few years now.
“I’ve been watching it closely for leaf mines of Liriomyza phloxiphaga (Agromyzidae), which is known from a single specimen I reared from phlox in my mother’s garden three years ago. No luck so far, but on August 17 I did find this:
“Leafminer #153: A heretofore unknown leafminer that forms a narrow linear mine in leaves of garden phlox, soon entering the midrib and presumably continuing into the stem—as with Marmara viburnella, but this isn’t a Marmara; at this point I’m not sure what insect order it belongs to. I can’t see an eggshell at the beginning of the mine, there is no evident frass or larva when I backlight the leaf, and there is no external evidence of feeding in the stem.
“I’ve found one other example so far, right next to the garage.”
In the 30th installment (two months later), I included this update:
“On October 11, I finally collected the mysterious Leafminer #153, which forms a short mine in a leaf blade of garden phlox before disappearing into the midrib and, I surmised, completing its development as a stem borer without leaving any further external evidence.
“I split open a couple of stems that had mines like this, and sure enough, something had been tunneling in the pith:
“Since the mine isn’t really visible in the leaf midrib and since the midrib and stem are difficult to dissect cleanly, I wasn’t able to see the mine actually transitioning from the leaf to the pith of the stem, but I confirmed that there was no tunneling in the stem immediately above a mined leaf but there was a tunnel right at the node with the mined leaf. I didn’t want to break apart too many stems for fear of damaging the larvae or pupae that I hope are still inside, but it seems that the tunneling continues all the way to the ground. Hopefully I got enough of the root to capture the mystery bug, and will be able to see who comes out in the spring.”
Nothing ever emerged from that stem, but in the spring I watched the phlox plants closely, and on May 27 I noticed the mines had appeared:
This example shows something that was also evident in the one I had found by the garage in October: associated with the mine are a bunch of little dots, which are “host-feeding” punctures a female agromyzid fly makes with her ovipositor, not for the purpose of laying eggs but to drink the juices that bubble out of the wounds—for nutrition and, I imagine, to “taste” and confirm that it is a suitable leaf to lay eggs in.
Not only did I see this strong circumstantial evidence that an agromyzid was responsible, I actually got to see several females making these punctures on the same day.
A shiny, metallic agromyzid fly whose larva lives as a stem borer is likely to belong to the genus Melanagromyza, which I don’t know much about because none of them are supposed to be leafminers. I collected one and sent it to Owen Lonsdale, even though I was pretty sure all he would be able to say was yup, that’s a female Melanagromyza, and we need to see male genitalia to get it to species—which is exactly what happened.
In July 2021, I uprooted a few mined phlox plants and put them in a clear garbage bag, but the only fly that ever appeared in it (in early September) was this “little house fly,” Fannia canicularis (Fanniidae):
In May of 2022, I split open a couple of the previous year’s phlox stems and found an empty Melanagromyza puparium in one of them—so the larvae evidently don’t always make it into the roots.
Nevertheless, most of the tunnels in the stems I split did go all the way to the ground. So that fall, I marked several plants that had leaf mines on them, and last April I dug two up, bagged them, and put them in the corner of my office to keep an eye on. (This, and what happens next, may look familiar if you’ve been following this blog for a while.)
Over the next several weeks, the tiny creatures that appeared in the bags included this 8-mm jumping spider (Salticidae: Phidippus princeps)…
…lots of dark-winged fungus gnats (Sciaridae; this one was <2 mm long)…
…this 5.5-mm soldier fly (Stratiomyidae), which is Allognosta fuscitarsis, the same species I once reared from a larva that had apparently arrived on the kitchen counter by way of a zucchini from the garden…
…and at last, a 2-mm male Melanagromyza! Somehow I sensed that this would be the only one, and I was worried I would lose it if I tried to get a live photo, so I chickened out and put it in the freezer first.
This winter, Owen and I have been working on a paper that deals with all the specimens I sent him through 2022, saving the 2023 specimens for a future paper. But since we were already describing a new Melanagromyza species John van der Linden had reared from a different phlox species in Iowa, it made sense for him to have a look at this specimen too. His assessment: another new species! I’ll reveal its name once that paper is published.
But wait, there were still more things appearing in those bags, like this ~2.5-mm “dusky lady beetle” (Coccinellidae, tribe Scymnini)…
…this ~1.3-mm spider, which I think is an Agroeca (Liocranidae)…
…this ~1.7 mm beetle (another Stilbus)…
…several ~1-mm spiders I can’t identify, and for which no one on BugGuide has suggested IDs yet…
…this ~1.2 mm “pleasing fungus beetle” (Erotylidae: Toramus pulchellus)…
…this ~1.5 mm “dirt-colored seed bug” (Rhyparochromidae: Antillocoris)…
…more and more dark-winged fungus gnats, which are consistently difficult to photograph alive, but I managed with this 3-mm long one…
…a bunch of little blackish slugs (Agriolimacidae: Deroceras)…
…this 4-mm casebearer moth larva (Coleophoridae), probably a species in the goldenrod-feeding Coleophora duplicis complex…
…this 5-mm wolf spider (Lycosidae)…
…this 5.5 mm ichneumonid wasp (tribe Phaeogenini; larvae are internal parasitoids of caterpillars)…
…this 2.4 mm eulophid (tribe Entedonini; similar to some of the ones that parasitize leafminers)…
…this ~2-mm agromyzid fly, which I think is something in the Phytomyzaatomaria species group; possibly P. crassiseta, which mines leaves of speedwells (Plantaginaceae: Veronica spp.)…
…still more dark-winged fungus gnats…
…a ~1-mm encyrtid wasp…
…another eulophid wasp, maybe the same as before…
…this click beetle (Elateridae: Melanotus)…
…this figitid wasp, which would have emerged from some kind of fly puparium, but it doesn’t look like the ones I rear from agromyzids; we’ll see what Matt Buffington has to say about it, eventually…
…another wolf spider…
…and finally, between June 4 and 10, nine of these ~2-mm frit flies (Chloropidae: Rhopalopterum):
I might not have thought much of these frit flies, but as it happens, in early April I split open a phlox stem right next to the garage and found three fly larvae near the base. They weren’t producing distinct tunnels as the Melanagromyza larvae do, but definitely living inside the stem.
All three formed puparia between the two layers of the piece of double-ply toilet paper I stuffed into the bottom of the vial I collected that chunk of stem in, and they emerged as adults between May 19 and 23.
To me they looked the same as the nine flies that emerged from the bagged phlox plants, and I sent them all to George Foster, who happens to be working on a revision of the genus Rhopalopterum. He agreed that they are all the same, and last I heard he was thinking they are a new species—the only new species he had encountered in the course of his revision. I will post an update when we have the last word on that, but I’ll add that I think this species has more than a casual association with garden phlox, because in July 2017, when I was investigating the leaf mines in my mother’s garden that turned out to be the work of the agromyzid that Owen and I later named Liriomyza phloxiphaga, I collected a few tiny flies that I found resting on the leaves, thinking they might be agromyzids—and they, too, turned out to be this same Rhopalopterum species.
When I decided to start working on a guide to North American sawfly larvae, the first thing I did was put together an updated list of all the species that occur here (the most recent list was published in 1979), so I could start taking stock of what was known about the host plants and larvae of each species. With this list completed, I discovered that there were eleven pairs of species that had identical names, all the result of a paper published ten years ago* that did away with several genera—including Amauronematus, Eitelius, Pachynematus, Pikonema, Pontania, Pteronidea, and Phyllocolpa—and declared them synonyms of the now enormous genus Euura, which now includes over 25% of the North American species in the largest sawfly family, Tenthredinidae. This is a shame, because many of these genera were convenient groupings; for instance, larvae of Pikonema species ate spruce needles, Pontania species all made round leaf galls on willows, Phyllocolpa species made leaf-fold galls on willows and poplars, and as previously defined, Euura contained two subgenera, of which one formed willow bud galls and the other formed willow stem galls.
In any case, when a similar change was made with agromyzid flies, lumping Chromatomyia and some other genera in with the now enormous genus Phytomyza, the paper that did so** included a complete list of all the world’s Phytomyza species and established new names to deal with the ten pairs of species that now had identical names as a result of this change. It seemed like no one was planning on doing this for the sawflies anytime soon, so one day last year I dashed off a little paper to take care of it myself, and that was just published yesterday***. All of the new names are based on the original ones; some are meaningless anagrams and for the rest I just changed the endings, as follows:
Amauronematus orbitalis Marlatt, 1896 →Euura borilista Eiseman
Euura minuta MacGillivray, 1914 →Euura untima Eiseman
I have never met any of the above species, but there was one more change I needed to make, and it involved a species I’ve found in my own front yard—the third type of sawfly larva I found in 2020 when I kept a running list of all the sawfly larvae and leafminers in my yard. I found five of these larvae munching on leaves of a bigtooth aspen sapling on May 31…
…All of them burrowed into a jar of soil the next day, and emerged as adults like this one the following spring:
Dave Smith identified these adults as the species that Marlatt had described as Amauronematus dyari in 1896 (named after Harrison Dyar, who is apparently the only person to have reared this species before me). When Dave put together the 1979 sawfly list, he placed this species in the genus Nematus, and because Marlatt (1896) had named another species Pteronus dyari that was later determined to be a synonym of Nematus latifasciatus Cresson, 1880, Dave established a new name for Amauronematus dyari, Nematus attus. The recent checklist of Canadian sawflies**** listed this species as Euura attus, as does the Electronic World Catalog of Symphyta, but this is incorrect: Dave’s replacement name is no longer necessary, because while this species has been transferred to Euura, N. latifasciatus (and therefore its synonym Amauronematus dyari) is still placed in the genus Nematus. So according to the rules of the International Commission on Zoological Nomenclature, the species in my yard must now go by the name Euura dyari.
I never thought I’d get mixed up in this kind of nomenclatural shenanigans, but as it happens I also felt compelled to rename a spider in another little paper that was also published yesterday*****. I wrote about this species ten years ago, and it is responsible for this egg sac, which I found on the underside of a board on Nantucket:
In 1884, H. C. McCook coined the name Micaria limnicunae for this spider, but his description—which applied only to the egg sac and the spiderlings that emerged from it—was considered “worthless” by arachnologists, and M. limnicunae has been treated as a name that can’t be attributed to any known species. However, for reasons explained in my paper, I am now convinced that this is the same spider that N. Banks described in 1892 as Agroeca ornata. I therefore have declared that the correct name for this spider is Agroeca limnicunae, and A. ornata is a junior synonym (and therefore should no longer be used). In this paper I also reveal that the maker of the mystery egg sac at the top of this post is Agroeca pratensis, and that also goes for the one on page 45 of Tracks & Sign of Insects and Other Invertebrates that is attributed to “Micaria limnicunae.” (My paper also discusses the mystery egg sac that was discussed on pp. 42–43 and here, concluding that the genus Tetragnatha is in need of revision and that arachnologists ought to take egg sac characteristics into account when working out the species limits.)
And while we’re getting caught up on taxonomic matters, I should mention that I wrote or co-wrote the sections on Bucculatricidae, Gracillariidae, Heliozelidae, Nepticulidae, Opostegidae, and Tischeriidae in the new checklist of North American Lepidoptera that was published a few months ago******, in which Erik van Nieukerken and I declared the poplar leafminer Stigmella aromella (Nepticulidae) a synonym of S. populetorum, and Don Davis and I declared the beech leafminer Phyllonorycter restrictella (Gracillariidae) a synonym of the European species P. maestingella, and the magnolia leafminer Phyllocnistis magnoliella a synonym of the tuliptree leafminer P. liriodendronella. Which brings us to the sad fact that I have now subtracted more species from the list of known North American moths than I have added. And, as it happens, one of the three moth species I have named–this little beauty, Grapholita thermopsidis (Tortricidae)…
…has had its name changed to the much less pronounceable Ephippiphora thermopsidis after the new checklist came out*******.
There are, of course, hundreds of leaf-mining moths that have yet to receive their first name, but unfortunately dealing with those requires a great deal more effort than shuffling around the names of the ones that have already been described.
* Prous, M., S. M. Blank, H. Goulet, E. Heibo, A. Liston, T. Malm, T. Nyman, S. Schmidt, D. R. Smith, H. Vårdal, M. Viitasaari, V. Vikberg, and A. Taeger. 2014. The genera of Nematinae (Hymenoptera, Tenthredinidae). Journal of Hymenoptera Research 40: 1–69. [Available online here.]
** Winkler, I. S., S. J. Scheffer, and C. Mitter. 2009. Molecular phylogeny and systematics of leaf-mining flies (Diptera: Agromyzidae): delimitation of Phytomyza Fallén sensu lato and included species groups, with new insights on morphological and host-use evolution. Systematic Entomology 34: 260–292. [Available online here.]
*** Eiseman, C. S. 2024. New names for Nearctic species of Euura Newman (Hymenoptera: Tenthredinidae). Proceedings of the Entomological Society of Washington 125(2) [2023]: 264–267.
**** Goulet, H. and A. M. R. Bennett. 2021. Checklist of the sawflies (Hymenoptera) of Canada, Alaska and Greenland. Journal of Hymenoptera Research 82: 21–67. [Available online here.]
***** Eiseman, C. S. 2024. On the identities of some distinctive, suspended spider egg sacs (Araneae: Liocranidae, Tetragnathidae). Proceedings of the Entomological Society of Washington 125(2) [2023]: 278–284.
****** Pohl, Gregory R. and Stephen R. Nanz (eds.). 2023. Annotated Taxonomic Checklist of the Lepidoptera of North America, North of Mexico. Wedge Entomological Research Foundation, 580 pp. [Print book; available for purchase here.]
******* Hu, G.-L., J. Brown, M. Heikkilä, L. Aarvik, and M. Mutanen. 2023. Molecular phylogeny, divergence time, biogeography and trends in host plant usage in the agriculturally important tortricid tribe Grapholitini (Lepidoptera: Tortricidae: Olethreutinae). Cladistics 39: 359–381. [Available online here.]
I just noticed that I never bothered to mention here that I finished the second edition of Leafminers of North America last December. Apparently I quietly updated the page dedicated to that book and then went back to working on other writing projects, including my guide to sawfly larvae and various papers on leafminers and other herbivorous insects. Of course all of the leafminer book subscribers received the last installment of the second edition at that time, and I sent out the first monthly installment of the third edition last month. So if you’ve been meaning to subscribe, now is a good time! Details are on that page (or you can click the image of the book cover below), and it’s still true that you can have the whole first edition for as little as $5, as explained here.
Also, someone just asked if there will be a calendar this year, and yes, a box of them is on the way to me right now! As usual, I will send a copy to anyone who makes a donation of at least $30 (the amount WordPress charges me each year to keep this blog free of annoying ads) before the end of November, which you can do here (select “Send,” and then include your mailing address in the notes). In this year’s calendar, some months have a single full-page photo and some show an adult leafminer along with its larval mine.
Also, I will be back at Eagle Hill in Maine next summer, teaching a week-long “Leaf and Stem Mining Insects” seminar the week of August 4. Their 2024 schedule isn’t on their website yet, but I suspect it isn’t too early to get yourself a spot if you contact them about it.
And also, one reason that things have been pretty quiet on this blog lately is that earlier this year, Julia and I had a baby girl, Ayla (pronounced eye-la). But the main reason is that this summer, we took Ayla on a six-week road trip—during which she got to meet two other baby girls at the International Congress of Dipterology in Reno, Nevada, where I was invited to speak about leaf-mining flies, and she also got to hang out with some moth people at the Lepidoptera Course at the Southwestern Research Station in Arizona, where I invited myself to visit and speak about leaf-mining moths on our way home—and as a result I’ve been extra busy with work (and bug rearing projects) ever since. Here’s Ayla examining a columbine flower in Arizona and an “oak apple” gall in Oklahoma (she determined the latter to be crunchy and full of ants):
Now the reports I had to do for other people are in, and almost all of my bugs are put away in the fridge for the winter, so I expect BugTracks will become a little more active as I go through all my photos from this year. In the meantime, if you know your western and midwestern plants, I’d appreciate any help you can offer identifying the hosts of the leafminers I found this summer, which are all posted on iNaturalist. I’m slowly getting caught up with reviewing everyone else’s leafminer observations in the Leafminers of North America project; I’m up to early September now, with just 4300 or so left to go! iNaturalist’s “computer vision” AI has improved greatly in recognizing leafminer species, so that I now can often select the correct identification from a dropdown list of its top guesses, but of course what makes things most efficient is when the (human) observer has made an informed identification (e.g. by using my book) and all I have to do is click “agree” and move on. One of the projects I’m currently focusing on is another big paper on agromyzid flies with Owen Lonsdale, which will include a number of new host records, new distribution records, and new species based on specimens that various iNaturalist users reared when I asked them to follow up on some particularly interesting finds.
Okay, I think those are all my announcements for now!
You know those hairs that line the basal portion of the midrib on the lower surface of black cherry (Rosaceae: Prunus serotina) leaves?
Or the ones in the vein axils on the lower surface of many other tree leaves, like this black oak (Fagaceae: Quercus velutina)?
It turns out these are Acarodomatia! Which is to say, they are structures that evolved for the purpose of housing mites that benefit these plants, either by preying on tiny herbivores (e.g. other mites) or by feeding on pathogenic fungi. I just heard about this for the first time last night when James Trager accidentally sent me a message on Facebook, which caused me to see a link he’d sent me four years earlier that I’d missed until now. (Tip: if you want me to see something, send me an email; I often miss things on Facebook messenger. If you want to make sure I never hear something, leave me a voicemail.) That link was to this “In Defense of Plants” podcast, which I listened to last night; it features Gussie Maccracken talking about her work with fossils, including this paper that gives evidence of acarodomatia already existing around 75 million years ago. Googling “acarodomatia” turns up lots of other information, including this review paper which says (among other things) that these structures are found in about half of North American tree species. I’m a little annoyed that I spent almost 20 years in school and no one ever mentioned the existence of these things.
So, today I walked around the yard and plucked a few leaves that had acarodomatia on them, including the two pictured above, and had a look at them under the microscope. I didn’t see anything among the hairs of the black cherry leaf, but they provide an extensive hiding place and it would be easy to miss any mites that may have been there. When I looked at the ones in the black oak vein axils, I saw a little colorless mite go scrambling out of the second one I looked at, and the same thing happened with the third—I think they were disturbed by the intense light under the scope. I was unable to relocate them when I trained my camera on them, but I believe the spherical object at the center of this photo is a mite egg:
Leaves of striped maple (Sapindaceae: Acer pensylvanicum), it turns out, have nice cavernous retreats in the vein axils behind these hairs. There are several pairs of these acarodomatia along the length of the midrib.
The red maple (A. rubrum) leaves I looked at just had a single pair of tufts at the base of the midrib. This restricted real estate, it seems, improved my chances of spotting the resident mite. See it?
Okay, it’s pretty subtle, given that it’s extremely tiny (~0.2 mm long) and hiding behind a couple of hairs. Here’s a closer crop:
I got a few other photos of it as it ran around on the leaf veins; they’re certainly not good, but maybe sufficient for an acarologist to tell us approximately what kind of mite it is:
So, as with extrafloral nectaries, these acarodomatia are common structures that are often mentioned in botanical manuals (hairs in the axils of veins noted in this key, for instance), but bafflingly, no one ever bothers to point out what their purpose is.
It’s normally a little disappointing to find an ichneumon wasp in one of my rearing containers, since that generally means I failed to rear whatever insect I was trying to rear. So when this one appeared yesterday…
…I braced myself for the bad news as I checked the lid of the jar to see what sawfly larva I had collected sometime last year, kept provided with fresh leaves of its host plant, given a jar of soil to burrow into, and refrigerated over the winter, only to have it succumb to a parasitoid, leaving its identity as mysterious to me as if I had just taken a photo of it on the plant and left it to its fate. But I found that what I had scribbled on the lid was “10/1/22 hazelnut, parasitized, gone 10/2.” Which meant that I already knew it was parasitized when I collected it on October 1, and it burrowed into the soil by the next day—so not a big loss, and a minimal investment of effort on my part. As it happens, I had just made it up to October 1 in sorting through the photos I took last year, so I was able to quickly refresh my memory about who this sawfly larva was. But before I get to that, a little background on the hazelnut sawflies in my yard.
Although there are native beaked hazelnuts (Betulaceae: Corylus cornuta) growing wild around the edges of the yard, it is the hazelnuts we planted—Corylus ‘Medium Long’, which is thought to be a hybrid of American hazelnut (C. americana) and the European hazelnut (C. avellana)—that always seem to attract the sawfly larvae. Just about every year, these larvae show up and get to work defoliating them:
Both of the above photos were taken on September 2, 2016, and at the time I thought I was seeing different-aged larvae of the same species—in fact, they were filed together until today, when I realized the smaller larvae in the top photo belong to a different family (Tenthredinidae; tribe Nematini) from the spotted larva, which is in the family Argidae. It was the spotted larvae that I succeeded in rearing; adults emerged the following June, and Dave Smith identified them as Arge willi.
When I did a thorough inventory of the sawfly larvae in my yard in 2020, larvae of the first type showed up on June 21. I collected them but again failed to rear them; four parasitoids in the genus Ichneutes (Braconidae) emerged the following March.
And I found larvae of Arge willi starting on September 1.
Then, on October 10, I found this beauty (which is something in the subfamily Tenthredininae)…
…but I failed to rear it as well. I looked in vain for more larvae like this in October 2021, and then again this past October. Although no yellow-spotted larvae materialized, I did find yet another species that I hadn’t seen in my yard before.
I think these may be Hemichroa crocea, which normally feeds on alder (Alnus) but is occasionally found on birch (Betula) and hazelnut (Corylus). I was just about finished writing my key to birch-feeding sawfly larvae this winter when I turned my attention to a taxonomic paper on tischeriid moths, but hazelnut will be the next key I do when I get back to that project (well, after musclewood (Carpinus), as I work my way alphabetically through the birch family). Anyway, on the same bush as the larvae above, I found this one, which (based on my knowledge of birch-feeding sawflies) I believe is a Nematus species.
I saw the objects attached to its head and thorax and knew it was unlikely to survive, but I decided to collect it anyway. Ichneumon wasps in the subfamily Tryphoninae attach stalked eggs to their hosts, and I think that’s what the brown object on the head is. As for the white object on the thorax, I believe it is a larva rather than an egg, but whether it’s a tryphonine or something else, I’m not sure.
In this view, the stalk on the egg is more apparent:
I think the ichneumonid that emerged yesterday is in fact a tryphonine, but someone please correct me if I’m wrong. And its sawfly host may have been Nematus corylus; for comparison, here are some larvae of that species that Julia and I collected on Nantucket in September 2020…
…and an adult that emerged the following April:
Looking back through my photos, I think N. corylus was probably the host of the braconids, and it may have been the species that I initially mixed up with Arge willi, but I don’t seem to have photos of those larvae in later instars. Once I put together my key to larvae on hazelnut I’ll have a better sense of how many (known) options there are for larvae with that general appearance. In any case, it’s nice to have our hazelnut bushes providing food for at least four different sawfly species, in addition to occasionally giving us some nuts to eat.
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For my Leafminers of North America project, I periodically need help identifying hostplants I find in my travels. You can peruse photos of them at iNaturalist. Thanks!
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