The online “Bugs in Winter” course I mentioned a few weeks ago is now full, because a limited number of people can participate in the live discussion sessions. However, the course content is now also available as an “on-demand” purchase; the only difference for people doing it this way is that they won’t be able to tune in to the live sessions (but they will still be able to watch recordings of them afterwards). As always, I will be available to answer any questions by email. For more information about the course, see this page.
The other, and more time-sensitive, announcement is that I’ve got some 2021 Leafminers of North America wall calendars available. These are normally reserved for my most generous patrons, but I will send one to anyone in the US or Canada who makes a contribution of $30 or more by midnight today (eastern time). $30 is the price I pay WordPress each year to keep this blog free of ads, so not a bad deal if you ask me! To make a contribution of any amount—which will go to support my continuing research into leafminers, sawfly larvae, and other obscure but fascinating herbivorous insects—you can use this link.
This year’s calendar includes some photos of leaf mines and some photos of adult insects I’ve reared from them. The cover photo (above) shows a white oak leaf with mines of three different moth genera: Stigmella (Nepticulidae), Cameraria, and Phyllonorycter (Gracillariidae).
Thanks everyone for your interest in my natural history ramblings, and I’ll see you next year!
As I do every winter, I’ve lately been picking away at organizing all the photos I’ve taken over the past year, and the other day I discovered that this blog’s running list of leafminers in my yard omitted a species I found back in July. It should have been #119 for the year, but we’ll call it…
Leafminer #209: Lyonetia prunifoliella (Lyonetiidae). On the evening of July 8, I collected some fresh pin cherry leaves for my attempted rearing of leafminer #70 (which I believe was Caloptilia invariabilis, but only braconid wasps ever emerged). One of the leaves had this vacated mine on it:
The fecal pellets strung like pearls on a strand of silk, dangling from a hole in the lower epidermis at the edge of the mine, easily identifies this as the work of L. prunifoliella. Young larvae of this species make narrow, linear mines with frass in a dotted central line, but this larva had wandered from its original leaf before establishing this blotch mine. Here’s an adult I reared from a pin cherry leaf I collected while teaching my leafminer course at the Eagle Hill Institute in Maine in the summer of 2019:
Might as well take care of some other loose ends while I’m at it.
Leafminer #210: Ophiomyia euthamiae (Agromyzidae), on grass-leaved goldenrod (Asteraceae: Euthamia graminifolia). This is another species (along with O. parda and Phytomyza erigeronis) that has my front yard as its type locality, and I was watching for it all year until I finally found a few mines at the southeast corner of the yard on October 23. The entire type series was reared from mines I collected in October 2015, so maybe this species just has one generation per year and larvae are only active in the fall, but the adults emerged from those mines three to six weeks after I took them out of the fridge in spring 2016, so one wonders what the adults are doing all summer. I guess it’s possible the eggs are laid in spring and early summer but don’t hatch until the fall, but as with so many things, further investigation is needed to figure out what’s really going on.
This species makes linear mines that are initially on the underside of the leaf…
…but then switch to the upper surface, where the blackish puparium is ultimately formed (upper left in the photo below).
Here’s another example from 10/23/2020:
And here’s the holotype from five years ago:
Once it started getting all snowy I figured that was about the end of this year’s leafminer list, but then on December 14 it occurred to me to check the young conifers at the edge of the woods.
Leafminer #211: Coleotechnites sp. (Gelechiidae), on hemlock (Pinaceae: Tsuga canadensis). There are two species with identical habits, of which one has green larvae (C. apicitripunctella) and the other has brown larvae (C. macleodi). The larva mines in one or two needles in the fall, overwintering in its last mine, and then in the spring it ties together several needles with silk, at first mining in them and later feeding on them externally. I haven’t yet found a larva inside a mine, but here is an abandoned group of tied and mined needles from last spring.
Seven years ago I managed to rear this adult of the brown hemlock needleminer:
Leafminer #212: Argyrotaenia pinatubana (Tortricidae), on white pine (Pinaceae: Pinus strobus). The larva of this species, the “pine tube moth,” ties a bunch of pine needles into a tubular bundle and then mines into several of them. It forms several of these bundles throughout its life, and in the last one, rather than mining the needles, it lines the inside of the tube with silk and then starts cutting off the ends of the needles one by one and then munching on them within the shelter of its tube. As with the hemlock needleminers, I haven’t yet found (or looked for) the young larvae, but the cut-off tubes of mature larvae are a common sight.
I was also keeping track of all the plants I ate in my yard this year, so here’s the final report on those.
The 130 plant species I ate belonged to 47 different families, the most important being Asteraceae (14 species), Rosaceae (13 species), and Brassicaceae (10 species). The 212 leafminers (representing 18 moth families, four families each of flies and beetles, and two sawfly families) collectively fed on plants in 52 different families, but no one species was found on more than two plant families. As with me, Asteraceae was the most popular family with the leafminers, supporting 39 species, followed by Rosaceae (35 species), Fagaceae (18 species), and Betulaceae (15 species). The 49 different types of sawfly larvae I found (including both leaf-mining and free-living species) were found on plants in 16 families, with 13 of them on Rosaceae, 11 on Betulaceae, four each on Fagaceae and Salicaceae, and just one on Asteraceae. For whatever that’s worth.
I’d never seen these “hammerhead flies” (Diopsidae: Sphyracephala) before this summer, but I encountered them several times in August while walking along streams. I’m not sure why they would be associated with streams specifically; apparently the larvae feed on decaying vegetation, and according to Steve Marshall’s Insects: Their Natural History and Diversity, adults are found in “swampy areas”; one of the two North American species, S. brevicornis, “overwinters in the adult stage and can often be found around skunk cabbage in early spring or late fall.” That’s all the information I’ve found about them so far. Here are some congregating on a leaf overhanging the Mill River on August 20:
Maybe someday I’ll meet them when I have a proper camera/lens in hand, but for now, this is what we get.
Despite its limitations, I’m loving this camera’s (the Olympus Stylus TG-4) ability to take pictures underwater. I wish I’d had back when I was spending every spring conducting surveys of vernal pool amphibians. Here’s a crayfish in another stretch of the Mill River, also on August 20:
Later that day, on the North Branch of the Manhan River, the pupal skin of a big crane fly (Tipulidae) poking out of the liverwort-covered streambank:
This crane fly I found ten minutes later may or may not have been what emerged from that pupa:
On the way back to the car from that site we met this American pelecinid wasp (Pelecinidae: Pelecinus polyturator). The larvae of this species are parasitoids of the grubs that turn into junebugs, or May beetles, or whatever you want to call them.
There was a little stream in Whately that was almost totally dry on our second visit, but when we came for our final visit on August 20 there was more water than ever. Lots of millipedes were congregating on emergent stones, seeking higher ground…
…and some that had chosen the wrong stones were still clinging to them underwater.
This group was joined by a slug. I don’t know how long these things can survive underwater, but it seemed like the water level must have gone up shortly before we arrived.
August 21, along the Middle Branch of the Westfield River: a dobsonfly egg mass attached to an overhanging boulder.
And a nice bit of exposed bedrock in the riverbed.
Later that day, I found a few larvae of the sawfly Tenthredo grandis (Tenthredinidae) on their host plant, turtlehead (Plantaginaceae: Chelone glabra), along the shore of the Whiting River.
I hadn’t seen one of these beauties in 16 years, so of course I brought a couple home for some better photos.
August 22, along Clesson Brook: a caddisfly infected with the fungus Erynia rhizospora, which causes its hosts to die plastered to rocks overhanging streams, aiding the pathogen in spore dispersal.
This crane fly has succumbed to a similar fate, presumably infected by a different fungus that is specific to crane flies.
And this fungus victim appears to be a yellowjacket or something like that. There seems to be a fungus for just about everybody, as evidenced by this gallery I’ve been maintaining on BugGuide over the years.
August 24, on the East Branch of the North River: a boulder that has been popular with the dobsonflies over the years. Each of the ~30 white rings is the remnant of an egg mass (like the one above) that contained up to 1000 or so eggs.
Here’s a close-up of the main cluster:
Please correct me if I’m wrong, but I’m thinking this is the shed skin of a caddisfly pupa that wriggled out of its case and crawled up the side of a boulder so that the adult could be out of the water when it emerged.
Later that day, somewhere in Rowe: eggs of a caddisfly (Limnephilidae) in a jelly matrix, deposited on a mossy bank overhanging a stream, into which the larvae will drop when they hatch.
Also a red eft (the terrestrial juvenile stage of the eastern newt)…
…and a footprint of a small black bear.
As it happens the next site we visited that day was the Cold River in Florida, where we’d seen a bear during our first visit. This is the slope we’d watched the bear scrambling up a few weeks earlier:
August 26, another big footprint—this one left by a beaver on the bank of the Konkapot River.
A mayfly resting by the Green River in Great Barrington (I’m told it’s Isonychia bicolor, same genus as the exuviae in my previous post):
And this was news to me: a native insect (the caterpillar of the pearly wood nymph, Noctuidae: Eudryas unio) that feeds on purple loosestrife (Lythraceae: Lythrum salicaria). It also feeds on the native swamp loosestrife (Decodon) and members of the evening primrose family (Onagraceae).
Along a little stream in Lenox, some sawfly larvae devouring a willow leaf (these, too, were added to the menagerie in jars on my desk):
Along the East Branch of the Housatonic River, a black and yellow mud dauber (Sphecidae: Sceliphron caementarium) on its way to daub some mud:
August 28, last visit to the Fort River: Sometimes it was hard to picture how a dragonfly nymph managed to get itself to the spot where I found its empty skin clinging, like this one that was at the tip of a long root dangling over the water:
Along the Middle Branch of the Westfield River, another caddisfly egg mass—this one more recently deposited (in the first one the eggs didn’t look as round because the embryos were pretty far along).
And that’s a wrap! (Well, there were some other interesting leaf mines, but I’ll wait till I have the full story on those.)
For the dragonfly survey this summer, Julia and I selected 30 sites and visited them each three times, so it was a busy six weeks of zigzagging all over the place from Florida to Monterey. (Yes, those are both towns in western Massachusetts.) It was along the Cold River at the Florida site that we got a good look at a bear during our first visit on July 26. When we returned on August 10, we got to see something equally thrilling but on a smaller scale: the intricate net constructed by a net-spinning caddisfly larva (Hydropsychidae). The function of this net is to catch food (algae, detritus, bugs, etc.) as it is swept downstream, so these are only found in reasonably fast-moving streams. I had the camera ready this time, but because the net was just below the turbulent water surface, getting a picture of it in focus was challenging. This is the best shot I (or maybe Julia) was able to manage:
But the camera did a reasonable job of staying in focus when in video mode, so you can get a better sense of the shape of the net here:
There seems to be a little larva in the right edge of the net in addition to the larger larva in the middle, which presumably made the net. Not sure what that other one might be. Here’s another attempt:
Later that day, in the East Branch of the North River in Colrain: Other insects were shedding their skins on the banks and emergent stones besides the dragonflies we were after. Here are the exuviae of a mayfly (Isonychiidae: Isonychia) and three water striders:
And a stonefly:
There is some kind of caddisfly that makes cases out of pebbles and gets together in big aggregations on the sides of rocks—maybe just when the larvae are getting ready to pupate.
A handsome green frog:
August 11, along a muddy stretch of the Konkapot River: a leaf of red osier dogwood with rows of dark spots indicating where sawfly eggs were inserted.
Spotting dragonfly exuviae on vegetation was trickier than on rocks, but I noticed this one’s face peeking out among the pinnae of a sensitive fern frond.
Later that day in the East Branch of the Housatonic River, some artwork created by a bird (heron?) standing on the tops of curved boulders and pooping.
We packed in five sites that day, and at the last one we were rewarded with dinner: oyster mushrooms…
…and chicken of the woods.
Also at this site was a green frog perched atop a tall, steep-sided boulder. I don’t really understand how it got up there.
A fancy adult caddisfly…
…and on the shore, leaf mines of Ophiomyia congregata (Agromyzidae) on rattlesnake-root (Asteraceae: Nabalus). By watching individual plants in the woods behind my house a few years ago, I determined that this the larva of this fly starts mining leaves in midsummer, then overwinters in the crown of the plant, mining into the petioles of new leaves in the spring and ultimately pupating there.
August 13, along the murky Fort River: Leaf mines in beggar-ticks (Asteraceae: Bidens sp.) made by Liriomyza carphephori (Agromyzidae), a species I described with Owen Lonsdale and Tracy Feldman last year. There are three larvae in this leaflet, visible as yellow dots toward the base.
At the same site, some monkeyflower (Phrymaceae: Mimulus ringens) in bloom, with what I assumed at the time was a leaf mine of Ophiomyia mimuli (Agromyzidae), a species I described with Owen Lonsdale two years ago—and I’m still thinking that’s probably right, but later in August I discovered there is another option on this host plant. More on that later…
Later that day, we met this distinctive moss along the Swift River. The auto-ID function on iNaturalist suggests it’s a Fissidens, which seems plausible but I really have no idea.
Okay, that’s how far I got with the photos yesterday. Maybe I’ll finish today?
Looks like it’s been a month since my last post. In that time I’ve made some great progress on my new guide to sawfly larvae (finished the preliminary literature review and ready to start putting together species accounts); revised and updated another chunk of the leafminer guide (I’ll be sending out the chapters up to and including the legumes shortly); and I’m now putting together an online course about how insects and other invertebrates make it through the winter (you can check that out here—apparently it’s almost full already, but if more people sign up we’ll add another session).
But right now I have to take a little break from all those things to put together a report that’s due at the end of the year. This summer the Massachusetts Natural Heritage & Endangered Species Program hired me and Julia to conduct surveys for an uncommon dragonfly, the ocellated darner. Our surveys consisted of slowly walking up 100-meter stretches of streams and small rivers, collecting all the exuviae (shed skins) left behind by emerging dragonflies when the nymphs crawled out of the water and molted to adults (as shown here). This fall, Julia got to go through all the exuviae we collected and identify them to species, and then enter all our data into a database, and now it’s my turn to work on putting the report together and submitting our data to NHESP. Part of that is going through and organizing all the photos I took of our survey sites. And part of that process is weeding out the “extracurricular” photos. So here’s the first batch.
July 24, Middle Branch of the Westfield River: Cimbex americanus (Cimbicidae), among the chunkiest of all sawflies, rests on a stone at the edge of the river, apparently having just emerged from a harrowing tumble down the river, which claimed parts of its left antenna and wing. This species is known as the “elm sawfly,” but it is actually one of the few sawflies whose larvae feed on foliage of a variety of unrelated trees.
July 27, Whiting River: A leaf of some kind of beggar-ticks (Asteraceae: Bidens) bejeweled with dew, and sporting a leaf-mining larva of a species of Calycomyza (Agromyzidae)—possibly C. avira, which Owen Lonsdale and I described two years ago.
Just a few feet away, some leaf mines on purple-stemmed aster (Asteraceae: Symphyotrichum puniceum) made by larvaeof Microrhopala xerene (Chrysomelidae), a striking black beetle with red racing stripes.
And dotted along the shore of that same stretch of river were mines on miterwort (Saxifragaceae: Mitella diphylla) made by what is probably an undescribed species of Phytomyza. (Julia and I collected and reared this species in Iowa last summer but Owen hasn’t had a chance to examine the specimens yet.)
I mostly had been leaving the camera in my backpack at this point in the season, but on this day I decided to keep it in my pocket to get a few pictures of the dragonfly exuviae in situ. The first one I came to was from a nymph that had climbed several feet up a hemlock tree to make its transformation. Some time after the adult had emerged, the shed skin had fallen and become caught in a spider web, and a gypsy moth was now laying her eggs behind it.
This stream had a population of green frogs that liked to hang out on ledges many feet above the water level. There is one tucked into a corner just above the middle of this photo, looking right at the camera.
Here’s how we often found the exuviae: clinging to the mossy ceilings of overhanging rock ledges. If you look closely at this skin you’ll see a little orange gall midge (Cecidomyiidae) resting on its abdomen.
July 27, Hubbard River: At the downstream end of this transect (where I had to stand and hold the measuring tape while Julia measured out 100 meters), there was a lovely sedge-covered island with a big patch of cardinal flower (Campanulaceae: Lobelia cardinalis).
Also on this island was a big witch hazel (Hamamelidaceae: Hamamelis virginiana) covered with galls caused by an aphid, Hamamelistes spinosus. Evidently these galls drip with honeydew, because the bush was abuzz with bees and wasps visiting the galls as if they were flowers. My little pocket-sized point-and-shoot was no match for these bugs that were in constant motion, but the photos below give you some idea. I think this first one is a potter wasp (Vespidae: Eumenes, or so)…
…and there were lots of common eastern bumble bees (Apidae: Bombus impatiens).
After we finished each survey, it was my job to walk transects across the stream and (among other things), at regular intervals, measure the water depth and characterize the substrate. On one of the points along my first transect on August 6, the substrate was a wood turtle! This is another uncommon species that NHESP keeps track of, so I ran the 100 meters back to my backpack to get the camera. I had never used this camera’s underwater mode before, but it went pretty well:
From that point on, I kept the camera in my pocket at all times, so the pictures of miscellaneous bugs and things became more frequent. Had I started doing that a week earlier, I could have also gotten pictures of a bear scrambling up a steep slope overlooking one of the streams we surveyed in the Berkshires.
August 6, North Branch Manhan River: a fishing spider (Pisauridae: Dolomedes vittatus) resting on a vertical rockface.
Hard to appreciate the size of this spider without something for scale:
And a side view reveals that she was carrying an egg sac under her body:
August 9, back on that the stretch of the Whiting River that had all those nice leaf mines and frogs: shortly before we arrived, a wading great blue heron had stepped out of the water and left these wet footprints across a boulder.
Also at that site, I met a strange fly I’d never seen before. I called it a “hammerhead fly,” which turned out to be on the right track: it’s a “stalk-eyed fly” in the genus Sphyracephala (Diopsidae), which is Greek for “hammerhead.” The “stalk-eyed” name is better applied to diopsids found in other parts of the world, as seen in this Wikipedia article.
Later that day, back at the stretch of the Hubbard River with all the cardinal flowers and witch hazel galls: a shed skin clinging to the underside of a totally mossless rock. It’s amazing to me that the nymph was able to cling upside down to this surface at all, let alone stay there for an hour while an adult dragonfly slowly squirmed out of its back, and then continue to cling there as an empty husk for days afterwards.
That’s how far I got as I went through the summer’s photos last night. More to come!
Fringed loosestrife (Primulaceae: Lysimachia ciliata) is a common plant of moist areas that, I realize now that I’m starting to write this post, I’ve never bothered to photograph. But it has yellow flowers and is related to garden loosestrife; it has nothing to do with purple loosestrife (Lythraceae: Lythrum salicaria). Anyway, five years ago—on September 22, 2015—I was at work doing some botanical something-or-other in a Massachusetts wetland when I noticed what appeared to be leaf mines on fringed loosestrife.
It took a very close look at the lower leaf surface to determine that they were in fact what I call “pseudomines”: rather than feeding between the two leaf epidermises—the definition of leafmining—the larva was feeding externally on the underside of the leaf, but beneath a sheet of silk that to the naked eye appeared to be the loosened lower epidermis of the leaf.
There was a twist though: although the “blotch” in the leaf blade was a pseudomine, the larva was also making a bona fide tunnel in the midrib. The entrance to this tunnel is visible at the left end of the pseudomine in the photo above; in the backlit photo below, the excavated portion of the midrib is transparent, and you can see the larva inside the midrib at the left end of this tunnel.
I tried to rear these larvae to find out what they were, and they eventually transitioned to feeding between leaves that they tied together with silk. I took photos of two of the larvae a month after I collected the leaves, on October 22.
Whether the differing appearance of the two larvae (e.g., the second one has darker spots and a dark prothoracic shield) indicates two different instars or just individual variation, I don’t know. By November 1, at least one of them had spun a silken chamber…
…which I suspect was a shelter in which to overwinter, rather than a cocoon in which to pupate. I don’t remember if any of the larvae survived the winter, but the photo above is the last one I have from this rearing.
This mystery has been bugging me ever since, compounded by my suspicion that this moth may be what V.T. Chambers described as Lithocolletis lysimachiaeella (Gracillariidae) in 1875*. The entire description of that species reads:
The larva is cylindrical and very small. It makes a very small tentiform mine on the under side of the leaves of (Lysimachia lanceolata) the loosestrife. The imago is, no doubt, very small—probably not larger than L. desmodiella, Clem., which is the smallest known species of this genus; but I have not succeeded in rearing it.
He gave no indication of where or when he found these larvae, but it was presumably near his home in Kentucky. When she revised the genus in 1908**, Annette Braun noted that she had never seen a Lithocolletis mine on Lysimachia**, and the species was essentially never spoken of again—until Brower (1984)*** made the baffling claim that three specimens had been reared from beech in Maine. (Some of the obvious misidentifications in his list of Maine Lepidoptera can be attributed to using old keys to identify species that hadn’t yet been described when the keys were written, but what could possibly have led him to believe that this species that was known only from a vague description of a larva was the same one that had been reared from a totally unrelated plant a thousand miles away?) The previous year, Don Davis had listed lysimachiaeella as a species of Phyllonorycter****, but this was based only on the fact that Lithocolletis had been synonymized with Phyllonorycter (though it’s not quite that simple, because Braun’s Lithocolletis subgenera Cremastobombycia and Porphyrosela are now recognized as full genera, and the genus Cameraria—which was named for V.T. Chambers; camera being the Latin word for “chamber”—was designated for “Lithocolletis” species with flat larvae that form upper-surface mines).
There is in fact no reason to believe that what Chambers described was even a gracillariid; just a few years earlier he had dedicated a whole paper to leaf-mining “moths” he had previously written about that had turned out to be beetles*****. There is also a footnote in (I think) one of Lord Walsingham’s papers where he listed some other egregious mistakes Chambers had made in describing new species based only on larvae, but I don’t remember now where I saw that.
Anyway, whether or not my midrib-tunneling loosestrife pseudo-miner is what Chambers called Lithocolletis lysimachiaeella, I’m reasonably sure it’s a moth in the family Tortricidae. A few tortricids in the genus Paralobesia do a similar combination of midrib tunneling and pseudo-mining in leaves of magnolia and tuliptree.
Last fall, on September 17, I found larvae of this mystery moth in Vermont, but I again failed to rear them to adults. I had a hunch that the larvae are immature when they overwinter and resume feeding as leaftiers in the spring, so on May 12 I was excited to see a bunch of tied leaves on the fringed loosestrife growing behind the chicken house.
(The frilly hairs on the petioles, incidentally, are why this plant is called “fringed” loosestrife.) Naturally I stuffed a bunch of these tied leaves in a peanut butter jar to see what the larvae would turn into. Alas, ten days later when I got a look at some of the larvae, I found that they bore no resemblance to the mystery larvae, though they did likewise seem to be tortricids.
At the end of May, the sparkling adult moths began to appear.
Identifying them turned out to be easy. The HOSTS database lists two moth species that feed on Lysimachia ciliata as larvae. One is Nola cilicoides (Nolidae), which I discussed as leafminer #157 in my yard list, and the other is Aterpia approximana(Tortricidae), which is a good match for the moths I reared. Which means, it seems, that nobody knows the identity of the species that was the main subject of this post. There’s always next year, I guess!
* Chambers, V. T. 1875. Tineina of the Central United States. Cincinnati Quarterly Journal of Science 2(2): 97–121.
** Braun, Annette F. 1908. Revision of the North American species of the genus Lithocolletis Hübner. Transactions of the American Entomological Society 34: 269–357.
*** Brower, Auburn E. 1984. A list of the Lepidoptera of Maine–Part 2: The Microlepidoptera Section 2 Cosmopterigidae through Hepialidae. Maine Agricultural Experiment Station Technical Bulletin 114: 1–70.
**** Hodges, Ronald W. (editor). 1983. Check List of the Lepidoptera of America North of Mexico. The Wedge Entomological Research Foundation.
***** Chambers, V. T. 1872b On some leaf-mining Coleoptera. The Canadian Entomologist 4(7): 123–125.
The day after I wrote my last post, in which I discussed an oak leafminer I’d previously mistaken for Stigmella nigriverticella and mentioned that I’d been keeping an eye out for leaves with “green islands” blowing onto my driveway from the quaking aspen across the road, I found a couple of leaves that require me to follow up on both of those stories.
Leafminer #206: Ectoedemia sp. (populella group) (Nepticulidae), on quaking aspen (Salicaceae: Populus tremuloides). The storm on October 16 brought the leaf I’d been waiting for:
I wrote about these mines five years ago, but I’ve done some further investigation since then, which is reflected on pp. 1129–1130 of Leafminers of North America. To summarize, there are two species in North America that make identical mines on aspen leaves. The egg is laid on the petiole and the larva mines from there into the base of the leaf blade, where it forms an elongate blotch with frass along the sides. The area surrounding the mine remains green after the rest of the leaf has turned yellow, and the larva continues mining within this green patch after the leaf has fallen to the ground. One of the species that does this is Ectoedemia argyropeza, which is introduced from Europe and is now one of the most common nepticulids in northeastern North America. The adult looks like this:
The other species doesn’t have a name yet. The only reared specimens in existence came from a single tree about a mile down the road from my house, but their DNA matches that of adult moths caught in Alberta, Saskatchewan, and Manitoba. The adult of this undescribed species looks like this:
It is not a Stigmella, as Erik van Nieukerken initially thought based on the above photo; it is an Ectoedemia in the populella group (along with E. argyropeza and E. populella). And although I pointed out some apparent differences between the mines of these two species in my post from five years ago, more recently I collected 100 mined leaves from that same tree and carefully scrutinized each one to make sure the mine characteristics were consistent with those of E. argyropeza. The following spring, dozens of E. argyropeza adults did emerge (including the one in the first photo above), but then a few days after the last one emerged, a dozen or so adults of the undescribed species emerged. So unfortunately it seems that identifying these “green island” aspen mines to species requires either DNA analysis or rearing adults.
Back to the leaf I collected in my driveway four days ago, here’s a view showing the eggshell (far left) and the initial mine in the petiole leading into the blade:
Here’s a backlit closeup showing the small blotch mine within the green island. Nobody seems to be home…
…but these larvae are mostly nocturnal, hiding in the petiole during the day. In the photo below, taken this evening, you can see the larva munching away.
Leafminer #207: Stigmella nigriverticella (Nepticulidae), on red oak (Fagaceae: Quercus rubra). The real one this time. I think I had noticed this mine before (in the shrubby area between the main yard and the “nut orchard”), but had ignored it since I knew I’d already put S. nigriverticella on the list.
I of course have no idea at this point what the adult of the S. nigriverticella imposter looks like, but here is the actual S. nigriverticella reared from the mine on Nantucket shown in my previous post:
Over the weekend I put all of my rearing containers in the little fridge in the basement so I can forget about them for a few months. I checked them all one last time before doing so, and I found two adults of sawfly #41 from pussy willow—a female from one of the hatchlings I’d collected on August 31 (all of the larvae matured and burrowed into soil by September 15)…
…and a male from one of the eggs I’d collected on September 2 (all of those larvae burrowed into soil by September 18).
I also got one last parasitoid for the season, a eulophine eulophid from a Cameraria betulivora mine in a black birch leaf I’d collected on September 27.
Today I was wondering what was going on with those late-emerging sawflies. The vast majority of sawfly species overwinter as prepupae, and I don’t know if any overwinter as adults. But surely there isn’t enough time for another generation to develop before all the willow leaves are gone? I wandered over to the pussy willow shrub that had already endured two generations of sawfly #9, followed by three waves (if not distinct generations) of sawfly #41, the last of which attracted a number of ichneumonids. I didn’t see any activity on the few remaining leaves, but without the distraction of all those sawfly larvae, I noticed for the first time something that had been there all along:
Leaf (stem) miner #208: Marmara salictella (Gracillariidae). This is the type species of Marmara, described from Pennsylvania by J. Brackenridge Clemens in 1863, and one that I haven’t had the opportunity to rear yet. Something to keep an eye on next spring!
Things are starting to wind down here in central New England, plant-wise, but I’ve managed to add a couple more leafminers and one sawfly larva to the yard list since the beginning of October. Also several parasitoids have emerged, unfortunately from mystery miners I was hoping to rear to adults.
For instance, on October 1 or 2, this eulophid (a Chrysocharis, I’m pretty sure) emerged from one of my few puparia of the unknown Liriomyza on amaranth (leafminer #181).
And at the same time, this opiine braconid emerged from one of the few intact puparia I found of the unknown stem-mining Ophiomyia on Queen Anne’s lace (#179):
Leafminer #204: Aulagromyza luteoscutellata (Agromyzidae), on Morrow’s honeysuckle (Caprifoliaceae: Lonicera morrowii). On October 7 Julia and I were pulling up some unwanted plants along the boundary with the ATV neighbor and I found one mine that can be attributed to this species with reasonable confidence—it certainly isn’t A. cornigera, the only other honeysuckle miner I’ve found in the yard this year (#9). An ant or some other predator had chewed the larva out of the leaf before it could finish mining.
On October 10 I found this perplexing pair of mines on a red oak sapling behind the chicken house:
So far the mines were entirely linear, suggesting a Stigmella rather than an Ectoedemia, but the known oak-feeding Stigmella species have larvae that are either distinctly yellow or distinctly green. The only one I know of that has a larva with a central row of ventral dots like these is S. altella, which (in addition to having a yellow larva) forms a strictly lower-surface mine, whereas these mines were on the upper surface. (Stigmella altella does appear only October, though, and it’s one of the species I was hoping to find in my yard this month.)
On October 13, I found one of the larvae flailing about on the paper towel in the bottom of the jar, now mottled with pink and orange…
…and the other had spun a white cocoon on the side of the jar—further evidence that these weren’t Stigmella altella mining the wrong side of the leaf; that species has a brown cocoon.
Here are the completed mines:
The way the frass is scattered along the full width of the mine is reminiscent of Stigmella nigriverticella, which has a bright green larva. This prompted me to take another look at my photos of Leafminer #148, which I’d asserted was S. nigriverticella but has been bugging me all summer because the frass is much more densely packed in mines of that species. Also, now that I actually look at this confirmed S. nigriverticella mine from Nantucket, I’m reminded that that species has a much narrower and much more evenly widening mine:
I have little doubt now that Leafminer #148, whose mines I found already empty at the end of July, is the same mystery species I just collected by the chicken house. Here are the July mines for comparison:
All four of these mines share a feature that I don’t remember seeing in any other nepticulid mine: a short, dense, narrow central line of frass right before the frass starts to be scattered broadly across the width of the mine. All four of the mines also begin with an egg laid next to a major vein on the upper leaf surface and end with an exit hole in the lower surface. Is this a previously unknown species of Stigmella or Ectoedemia? One of those, I guess. We’ll see if I luck out and get an adult (or salvageable DNA) from one of these larvae. Whatever this turns out to be, it looks like I’ll have to add a 138th couplet to my key to North American oak leaf mines.
Also on October 10, I found the 49th distinct type of sawfly larva for this year’s yard list: a dazzling, solitary one on one of our cultivated hazelnuts (Corylus ‘Medium Long’), unlike any I’ve seen before on that plant.
On October 13, it molted to a prepupa and I transferred it to a jar of soil. When I checked yesterday it had burrowed down to overwinter and pupate.
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.
This next one isn’t from my yard, but worth mentioning: On October 12 I awoke to discover that a fly had emerged from one of the jars of soil I keep on the dresser next to the bed—the first sign of life there in several months. It turned out to be a Chirosia (Anthomyiidae) from a leaf mine on silvery spleenwort (Deparia acrostichoides) that Julia and I had collected in Vermont while on a field trip with the New England Botanical Club—on June 16, 2019! Usually there’s no point in keeping a jar of soil around for more than a year, and this one had completely dried out, but I’d been reluctant to give up on it because the single larva that had burrowed into it held the answer to a long-standing mystery that I haven’t had many opportunities to pursue.
So what species of Chirosia is it? I dunno, they all look like this. We’ll find out whenever Brad Sinclair gets to go back to work at the Canadian National Collection and I can send it to him.
Between October 10 and 12 (I haven’t been checking the rearing vials everyday lately because things have really slowed down), a braconid emerged from the Phyllonorycter kearfottella mine on Chinese chestnut that I’d collected on September 27 (#195). I think it’s a miracine:
Multiple times over the past few weeks, I’ve checked the black birch saplings in the “lower nut orchard” for leaf mines of Ectoedemia occultella (Nepticulidae). I’ve only found this species three times in the past decade, and never in my yard, but I’ve just felt like it should be here. And at least as often as I’ve been checking those birches, I’ve been checking our driveway (at the opposite end of our yard) to see if a leaf with one of the “green island” Ectoedemia species has blown in from the quaking aspen across the road. Yesterday, as Julia and I returned from a walk up the Crag, we stopped by the mailbox to look for the latter, and Julia spotted a leaf with a hint of a green island on it—but rather than blowing from the aspen across the road, it had fallen from the paper birch (Betulaceae: Betula papyrifera) at the edge of our own yard. The little bit of green on the otherwise yellow leaf marked the edges of an Ectoedemia occultella mine! So that’s Leafminer #205:
As you can see, this species makes a small blotch mine without any initial linear portion, bounded by two adjacent lateral veins, with a characteristic dark circle in the middle, on the underside of which the tiny, shining eggshell can be found.
It’s been a little while since I updated the list of plants I’ve eaten from the yard this year. Julia says I get to count potted plants on our deck and in the house, since the house is in our yard, so:
118. Ginger (Zingiberaceae: Zingiber officinale) – rhizome 119. Fig (Moraceae: Ficus carica) – fruit 120. Asian pear (Rosaceae: Pyrus pyrifolia) – fruit 121. Butternut squash (Cucurbitaceae: Cucurbita moschata) – fruit/seeds 122. Some sort of melon (Cucurbitaceae: Cucumis melo) – fruit
In my previous post, I mentioned having found a couple of leaf mines that needed a little more investigation to decide whether they’re something new for this year’s yard list. Well, I investigated, and they are!
Leafminer #197: Stigmella sp. (Nepticulidae), on paper birch (Betulaceae: Betula papyrifera). On September 27 I plucked a leaf with three narrow linear mines on it from the paper birch sapling at the southeast corner of the yard. I’ll show each of them in top, bottom, and backlit views. Here’s the first one:
The egg was laid next to a prominent vein on the underside of the leaf (lower left corner of the third photo above), but the mine is initially confined to the upper surface, following the vein (first photo above); later it becomes full-depth, visible on both leaf surfaces. The second mine follows the exact same pattern (note the eggshell in the upper left corner of the third photo below):
The third one starts out the same way (note how it starts out following a vein from the right edge of the first photo below, originating from an egg visible at the left edge of the third photo), but then it becomes a mostly lower-surface mine, with a few little full-depth patches.
The little dots of external “window feeding” on the underside of the leaf next to the third mine initially led me to think these were Bucculatrix mines (both birch-feeding Bucculatrix species form short linear mines that they exit to window-feed on the leaf surface), until I saw that all three larvae were still in their mines and realized this feeding sign was from some other insect. The round eggshells and the appearance of the larvae identify these miners as moths in the family Nepticulidae. Consulting the key I wrote to the known North American birch leafminers, I see that a linear mine like this could be the work of one of seven species, but I can rule out the three species of the Stigmella betulicola group because they have distinctly yellow larvae. This leaves two species in the S. lapponica group that are also known from Europe, plus an undescribed Stigmella in the lemniscella group and Ectoedemia quadrinotata, both of which I’ve already found in my yard this year (on black birch and hazelnut, respectively). All four of these have pale larvae like the ones in this leaf. Stigmella lapponica can clearly be ruled out because its mines are initially filled with green frass, whereas these mines have a black central frass line in the early portion.
Two days after I collected the leaf, all three larvae had exited their mines to spin cocoons. Here are backlit views of the completed mines:
Each of these mines is only about 0.5 mm wide at the end—probably the narrowest completed nepticulid mines I’ve seen on any host plant—and in each case the larva exited through a slit on the lower leaf surface. These mines are far too small and narrow for Ectoedemia quadrinotata, which I was already inclined to rule out because the larva of that species has a dark central spot on each segment that should have been visible in my photos. They are also too narrow, and the frass pattern is all wrong, for the undescribed species in the Stigmella lemniscella group. This leaves S. confusella, which is only known from Manitoba outside of Europe. Although that species likewise lays its eggs next to veins on the lower leaf surface, it is said to form “a very long and slender mine, with frass in a continuous, very narrow, central line. The mine follows veins over long distances, giving it an angular appearance.” These mines are certainly slender, but they are by no means “very long”; the frass tends to fill the later portion of the mine; and each only follows a vein at the beginning. They bear little resemblance to the examples shown on the European leafminer website. This is why, when using a key, it’s important not to just accept whatever identification you land on at the end. You should always read the accompanying description and consult whatever illustrations are available to make sure everything fits.
So what species have I got here? I dunno. Some other Stigmella, I guess. Another undescribed species? A European species not previously documented in North America? I look forward to hearing what Erik van Nieukerken has to say about these.
Leafminer #198: Ophiomyia carolinensis (Agromyzidae), on smooth aster (Asteraceae: Symphyotrichum laeve). Weeks ago I had noticed a mine of Acrocercops astericola (Gracillariidae) on this aster growing by the mailbox, and I for a while overlooked the O. carolinensis mine a few leaves up the stem from it because it was superficially similar. I had a nagging feeling about it and finally got around to taking a closer look yesterday. The way the mine alternates between leaf surfaces is characteristic.
Leafminer #199: Phytomyza crassiseta (Agromyzidae), on speedwell (Plantaginaceae: Veronica sp.). Julia and I noticed a few of these mines yesterday when we peeked under the ostrich ferns growing along the side of the garage to look for one of the little leatherwood shrubs we’d planted last year (it turned out a vole or rabbit had recently cut the stem off at the base for no discernible reason).
A backlit view shows the two puparia hidden on the lower surface, each with a longitudinal stripe on its belly:
Last night there were strong winds that woke us up in the middle of the night and made us wonder for a little while if we should go seek shelter in the basement. This afternoon I spent some time picking up branches that had blown all over the front yard, mostly from the big poplar tree at the south edge of the yard.
As I’ve been tallying the leafminers and sawflies in the yard throughout the year, I’ve been looking on this tree with a bit of scorn because it never seems to have any bugs feeding on it. It’s a weird tree that I’d never gotten around to trying to identify before today; it clearly was planted by the previous owners at the same time as a bunch of other oddball trees that are all smooshed together there at the edge of the yard: a silver maple, a pin oak, a pitch pine (which finally died in the past year due to competition with its neighbors), a European larch, and several nonnative spruces (a few of which we cut down several years ago to let some more light into the yard). After checking two botanical manuals, it seems to be Populus × canadensis, a hybrid between the native eastern cottonwood (P. deltoides) and the European/Asian/African black poplar (P. nigra). Today this tree finally started pulling its weight.
Leafminer #200: Aulagromyza ?populicola (Agromyzidae). Just after throwing a big branch on the brush pile, I noticed this mine on the underside of one of the leaves.
A close look at the backlit view below reveals the tiny puncture where the egg was inserted in the leaf; the scattered, fine specks of frass; and the two rows of meconial pillars arranged by a eulophid wasp larva after devouring the fly larva from within. The emerging adult wasp chewed a round exit hole in the lower epidermis between the two rows of pillars, which served to protect the wasp’s pupa from potential collapsing of the mined leaf tissue as it dried.
Aulagromyza populicola is a European species that has been found in Ontario and Oklahoma; this mine was either made by that species or something unknown but presumably closely related (A. populicola is not known to make lower-surface mines, which I’ve found before on cottonwood and bigtooth aspen in South Dakota, Kansas, and Massachusetts).
Leafminer #201: Stigmella populetorum (Nepticulidae)… or another, closely related species in the S. salicis group. I spotted this mine on the lower surface of a leaf on a twig that had blown all the way across the yard and onto the driveway.
Although at first glance this looks like another irregular whitish mine similar to the Aulagromyza one, the egg in this case is deposited on the leaf surface instead of inserted; the mine is initially narrowly linear; and the frass is in a continuous dark line (as in the Stigmella on birch).
Leafminer #202: Phyllocnistis populiella (Gracillariidae)—yet another lower-surface mine, this one on a big branch that landed on the hugelkultur bed. This superficial mine is formed just in the epidermal cells, and it appears silvery or nearly invisible depending on the angle of the light.
Leaf (stem) miner #203: Marmara fasciella (Gracillariidae), on the white pine (Pinaceae: Pinus strobus) sapling at the edge of the leach field. I’m pretty sure I checked this sapling back in the spring when I was on a roll with finding Marmara mines in the yard, but somehow I missed this mine, which clearly has been there all along.
I don’t expect to add too many miners to the yard list in the remaining three months of the year, but you never know…
An auspicious beginning for the fall leafminer season!
Leafminer #191: Ectoedemia populella (Nepticulidae), on quaking aspen (Salicaceae: Populus tremuloides). On the morning of September 22, I went to get the paper and noticed this leaf that had blown onto our driveway from a tree across the road:
The swelling in the petiole at the base of the leaf is an incompletely developed gall of E. populella, which naturally is known as the “poplar petiole gall moth.” Although this species spends most of its larval life feeding in the gall, it hasn’t forgotten its leafminer roots. A close look at the underside of the leaf reveals that the egg was laid on the leaf blade, and the newly hatched larva mined along the midrib and into the petiole before causing the gall to form.
I already had Coptodisca splendoriferella (Heliozelidae) as leafminer #135 back in July, when I found it on black cherry, but I couldn’t resist getting a shot of this nice group of mines on an apple leaf—some of the larvae are still feeding, while others have already cut out their oval cases and dropped to the ground in search of a place to pupate and overwinter.
Leafminer #192: Neochirosia nuda (Scathophagidae), on Canada mayflower (Asparagaceae: Maianthemum canadense). I noticed some mines of this fly on a walk in the woods, and I remembered there are some Canada mayflower plants growing along the north side of the shed. I checked them and sure enough, two of the leaves had mines. On the leaf shown below, there are eight brown eggs along the midrib, but only one of them has hatched so far.
Leafminer #193: Synchysa tricincta (Scathophagidae), on false Solomon’s seal (Asparagaceae: Maianthemum racemosum). This species lays white eggs on the lower leaf surface instead of brown eggs on the upper surface. I had been watching for its mines all year, and finally found one on September 22 on a false Solomon’s seal plant I hadn’t noticed before. The mine was probably formed months ago.
Leafminer #194: Calycomyza malvae (Agromyzidae), on hollyhock (Malvaceae: Alcea rosea). Three new leafminers for the yard on the first full day of autumn was already pretty good, but it suddenly popped into my head to check the pathetic little hollyhocks we planted in the shade behind one of the compost bins this summer, and sure enough, there were a couple of larvae mining away.
The next day Julia and I went to Nantucket for the 10th annual survey of leafminers, gallmakers, and other little-known herbivorous insects there. It was a very successful visit; I’ll have more on that sooner or later. We got home on the 26th, and when I walked around the yard the next day, there were a few more leaf mines to be found.
Leafminer #195: Phyllonorycter kearfottella (Gracillariidae), on Chinese chestnut (Fagaceae: Castanea mollissima).
Leafminer #196: Stigmella sp. (Nepticulidae), on Chinese chestnut. I’m not sure exactly what species this is (no North American species has been reported from Chinese chestnut), but it isn’t either of the Stigmella species I’ve found on oak in my yard this year.
I found a couple of other mines that need a little more investigation to decide whether they’re something new. For now, here are some other things I found as I wandered around the yard yesterday.
On September 6 I’d found these red-humped caterpillars (Notodontidae: Schizura concinna) on the underside of a leaf on the little aspen sapling in the front yard—I wrote that they were in varying stages of becoming “mummified” by braconid wasp larvae spinning cocoons inside them.
When I checked yesterday, I realized that these weren’t actually the caterpillar “mummies” characteristic of braconid wasps in the genus Aleiodes; the wasps here were campoplegine ichneumonids, which spin their cocoons outside their hosts but in some cases wrapped in the host’s skin.
Most of the wasps had already chewed their way out of the cocoons:
In this side view, you can see the white cocoons peeking out under some of the “pelts.”
Nearby, galls of Dryocosmus deciduus (Cynipidae) were bursting out of the midribs of leaves on a little red oak sapling (Fagaceae: Quercus rubra):
The larger red oak sapling in the “upper nut orchard” had some nice fuzzy midrib clusters made by another gall wasp, Callirhytis lanata.
The Tischeria quercitella mines I first noticed on September 5 are coming along nicely.
A little downhill from that oak, a third wave of sawfly #41, which I first noticed as tiny hatchlings, is continuing the work of defoliating the pussy willow (Salicaceae: Salix discolor).
Yesterday the shrub was abuzz with ichneumon wasps trying to lay eggs on these larvae.
They would fly within a few centimeters of the larvae and then turn around and approach them backwards.
Every encounter that I watched ended with the sawfly larva flicking its tail end and the wasp flying away—except in the case of the wasp in the photo above, which was actually knocked off the leaf by the larva immediately after I took the picture.
Back in the “upper nut orchard,” I noticed these elegant poop tubes on the undersides of a few hazelnut leaves; presumably the work of an Acrobasis species (Pyralidae).
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