Micro Fiber Art

I’m mainly writing this post because of one picture I wanted to share, but first I’ll provide a little context. In the moth genus Bucculatrix, most species start out life as leafminers, forming short linear mines. Bucculatrix locuples is typical in this respect, but is the only species known to feed on alders (Betulaceae: Alnus spp.). Here are vacated mines of two larvae (the one on the right is a little harder to discern because of brown splotches caused by an unrelated injury to the leaf):


After making these initial mines, larvae of most Bucculatrix species exit and spend the rest of their lives feeding on the leaf externally. Here again, B. locuples is no different:


And like its relatives, externally feeding larvae of B. locuples periodically spin flat, oval cocoons in which to molt. At first, the molting cocoons of B. locuples are white as in other species…


…but older larvae spin yellow molting cocoons:


Mature larvae of Bucculatrix species spin an elaborate, elongate cocoon in which to pupate; this is typically white and longitudinally ribbed. Before spinning this, some species first erect a ring of white silken pillars around the future cocoon site; the purpose of this fence is apparently to deter marauding ants, though I find it difficult to picture how it could be effective. In B. locuples, both the ribbed cocoon and the silk fence are made of dark brown silk, and I imagine the yellow tint to the final molting cocoon has something to do with the transition in the type of silk the larva is producing. I have always had a hard time photographing these fence-encircled cocoons due to the limited depth of field in macro lenses (and I’m too busy to bother with focus stacking), but the particular individual I was rearing this month spun its cocoon in a corner at the bottom of its vial (rather than on a flat surface as is typical), so that the pillars were bent toward each other and I was able to get a photo that gives a decent look at what’s going on:


So that’s all I wanted to show you. Oh, and today the moth emerged; it’s the first adult of B. locuples I’ve seen.


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On Monday I spotted these little eggshells on a tall blue lettuce (Lactuca biennis) plant growing under the black cherry (Prunus serotina) tree in my yard:


There aren’t many insect eggs I would identify to species with confidence, but these brown-rimmed hockey pucks were without a doubt deposited by a polyphemus moth (Antheraea polyphemus). This makes four giant silk moth (Saturniidae) species I have now found in my yard. Our first winter here (January 2014), I noted an old parasitized Callosamia promethea cocoon within ten feet of the spot where I found a caterpillar last week; one night in June 2018, an Actias luna adult came fluttering to the bathroom window; and this past winter I found a Hyalophora cecropia cocoon on a trellis in the middle of our front yard (I had previously found a caterpillar munching on birch leaves in the woods behind our house).

All of these are exciting to find in the yard, not just because they are big, fancy moths, but because giant silk moths have been in decline for decades. A major reason for this decline seems to be the parasitoid fly Compsilura concinnata (Tachinidae), a European species that was introduced to North America in 1906 to control gypsy moths (Lymantria dispar). Like many early biological control efforts, this was not well thought out; C. concinnata is an extreme generalist and is known to attack over 200 other insect species (it also isn’t particularly effective against gypsy moths).

On a related note, on Tuesday I found this group of eggshells while Julia and I were harvesting some dill in the garden:


These belong to another import, the multicolored Asian lady beetle (Coccinellidae: Harmonia axyridis). I know this not because the eggs are so distinctive but because the little hatchlings were crawling all over the leaves within a few inches of the eggshells. Here’s one of them chomping an aphid, as it was brought here to do:


Unfortunately, this is another generalist that eats not only all sorts of aphids, scale insects, thrips, and mites, but also eggs of butterflies and moths. In addition to annoying people by invading their houses in large numbers in the winter, this species has also largely displaced our native ladybugs. When this one landed on the lawnmower yesterday…


…I assumed it was one of those native species, but darn it, it turns out to be another European import, the fourteen-spotted lady beetle (Propylea quatuordecimpunctata). When I first saw it it was just beginning to munch on an aphid, but by the time I had run inside, switched lenses, replaced the flash batteries, and run back out with the camera, the aphid had been reduced to a little ball of mush with an antenna sticking out.

I found one other eggshell in my yard this week, and it was not a welcome sight: When I went to check on the promethea caterpillar on the cherry tree, it was looking a little sickly:


See that little white egg?


It’s a tachinid fly egg, which means there is a fly larva—likely Compsilura concinnata—feeding inside the caterpillar. Oh well; at least I know a few giant silk moths are somehow surviving to adulthood to produce the eggs and caterpillars I’m finding in my yard.

(A huge “thank you” to Sam Jaffe of The Caterpillar Lab, who made this post possible by generously lending me his macro lens while mine are being repaired!)

…Added the next morning: I just woke up thinking, “Wait a minute—Compsilura concinnata larviposits!” Females of that species insert larvae directly into their hosts, so this is the egg of some other (presumably native) tachinid. Although it doesn’t change the fact that this caterpillar is likely doomed, this makes me less disappointed to have seen the egg. I’d even be excited if it turned out to be a fly that specializes in giant silk moths, but I just checked the Host-Parasite Catalog of North American Tachinidae (Arnaud 1978), and the half dozen species recorded from Callosamia promethea are all generalists that could just as easily have settled for some run-of-the-mill caterpillar.

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Sharing the Fruit Trees

Periodically I am asked how to get rid of some bug or another. If I am giving a public talk, I want to reply, “have you not been paying attention to anything I’ve said for the past hour?” If the question comes in the form of a comment on this blog, I have to wonder what possessed the person, rather than asking any of the innumerable extension entomologists or pest control specialists out there, to instead ask the author of a website dedicated to celebrating the natural history of insects—it says “Bringing glory to Earth’s small and neglected creatures” right there at the top, for crying out loud.

For future reference, here is the sum total of my experience dealing with insect pests: When Japanese beetles are abundant in my yard, I walk around with a bowl of water (with a drop of soap added to break up the surface tension), knock them into it, and give them to my chickens. When cabbage white caterpillars are abundant on the broccoli or some other Brassica, I pluck them off and give them to the chickens. When the Pegomya leaf-mining flies show up on the spinach or chard, I try to eat the leaves before the eggs hatch or the larvae get too big; if I miss some, those leaves go to the chickens. That’s pretty much it.

Today I was delighted to find larvae of the beetle Baliosus nervosus mining the leaves of our cherry, plum, and medlar trees—all of these were previously undocumented hosts for this species, and the beetles confined their damage to less than one leaf per tree. I was mildly concerned when I saw this mass of tiny caterpillars on one of the plum trees:


I believe these are young larvae of Schizura concinna (Notodontidae), which I found four years ago on the neighboring cherry tree:


August 16, 2015


August 22, 2015

The next year I found some nearly mature ones busily defoliating our young persimmon tree:


September 4, 2016

These caterpillars are hungry and numerous, so they’re not the best thing to have on a fruit tree, but I don’t hold anything against them. Today, as before, I plucked the leaf they were on and moved them to a wild black cherry tree at the edge of the yard, which they can munch to their hearts’ content as far as I’m concerned. There, they were greeted by another caterpillar…


…which appears to be Acronicta radcliffei (Noctuidae). Also on that black cherry tree was this Callosamia promethea caterpillar:


(It was actually hanging head-down, but I rotated this photo 90 degrees to better fit the format of the blog.) Bigger (than 1 cm) moths are not my forte, and I confess to having initially mistaken this for a young cercopia. While I was out documenting the charismatic megafauna on my fruit trees, I figured I might as well get a shot of this caterpillar I’d spotted earlier in the day on the medlar:


This is another notodontid, Schizura unicornis, and it is quite dead—perched atop a logpile of cocoons spun by the microgastrine braconid wasp larvae that until recently were feeding inside it. Look closely and you’ll see that the side of its abdomen is riddled with their exit holes.

It’s just as well that the things I wanted to photograph today were on the large side, because this morning I sent my beloved MP-E 65mm macro lens off to the Canon Factory Service Center to be repaired. This was actually my second MP-E 65, which I’d bought as a backup when the first one developed the same problem, but apparently I’d never gotten around to sending the first one off to be repaired, so I actually sent both lenses off today. Hopefully I don’t come across anything tiny that needs photographing in the next couple of weeks, because I don’t think a third $1000 lens is in the cards for me.

One of the last things I was able to photograph before my backup macro lens gave up the ghost was this 1-mm entedonine eulophid wasp, which coincidentally also came from a caterpillar on a rosaceous fruit tree:


On Saturday afternoon, on my way home from teaching a week-long course on leafminers at the Eagle Hill Institute in Maine, I stopped at Mt. Wachusett in eastern Massachusetts to lead an insect walk at a BioBlitz event. The walk ended in an old orchard, where we found several species of leafminers on the apple trees, including underside tentiform mines like this one…


…made by a species of Phyllonorycter, likely blancardella. I collected a few mines to try and rear adult moths, and on Tuesday the wasp emerged from one of them. Yesterday after I had photographed the wasp, I located the mine that had an exit hole and opened it up to see what other evidence the wasp had left behind. I discovered that rather than being a primary parasitoid of the moth larva, this wasp had emerged from the cocoon of a microgastrine braconid wasp (in the genus Pholetesor, I believe), the larva of which was what had actually done in the leafminer.

Here’s a view of the braconid cocoon inside the Phyllonorycter leaf mine, with the eulophid’s exit hole toward the left end:


Had the braconid not been parasitized by the eulophid, here’s what would have emerged from that cocoon:


And had the moth larva not been parasitized by the braconid, here’s what would have emerged from the leaf mine:




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Complete leafminer guide now available!

This weekend I finished the first edition of my Leafminers of North America e-book—1857 pages long (plus a 54-page table of contents, 20-page glossary, and 68-page bibliography), and illustrated with thousands of color photographs. To purchase it or learn more about it, you can click this image of the cover.

Although the book is a “complete” guide in terms of including all previously published information about North American leaf mines—heavily supplemented with previously unpublished observations—I have, as expected, continued to find new things to add on an almost daily basis. Just last week, my third paper with Owen Lonsdale was accepted for publication; it will describe another ten new species of agromyzid flies. And just yesterday, I went on a successful mission to collect more larvae of this Calycomyza species, which appears only in early June, has only been found at a single location, and is so far known only from unidentifiable females (but almost certainly represents another new species):


As a bonus, on my way to look for that species, I discovered two new larval hosts for the adorable Orchestes pallicornis (Curculionidae).


So I already have plans to complete an updated second edition of Leafminers of North America by the end of 2020. My current thought is that I will release the first installment in January, so that I’ll have time to finish up a number of papers as well as get started on a brand new project: a hostplant-based guide to North American sawfly larvae (only 37 of which are leafminers, out of about 1000 species).


I will of course be posting more about that project as it gets underway. In the meantime, anyone who has purchased the full first edition of Leafminers of North America before the end of July 2019 (when I will be teaching my week-long leafminer course at the Eagle Hill Institute in Maine) will receive a free subscription to the second edition.

And for those who just want to contribute to my ongoing efforts to uncover natural history mysteries and share my findings with the world, there is always the “Make a Donation” button at the top of the right sidebar. If everyone reading this chipped in the same amount I do every year to keep this blog ad-free ($30), I could do this full-time! Thank you for reading, whether or not you are able to make a financial contribution.

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More charismatic megafauna

Although this blog is mostly devoted to tiny, obscure insects, once in a while I encounter something big and conspicuous that seems worth sharing. And so today I find myself writing a second consecutive post without any leafminers in it—though it was in search of an elusive leafminer of false hellebore (Veratrum viride) that I wandered over to the edge of a small brook this morning. There, perched atop a skunk cabbage (Symplocarpus foetidus) leaf, I spotted this dragonfly naiad:


After checking that it wasn’t just an empty skin, I decided to hang around for a minute and see if the adult started to emerge. Sure enough, one minute later I saw something bulging from the middle of its thorax.


Although my camera battery was nearly dead when I arrived, it managed to hang on throughout the ensuing spectacle, so you can now witness it in a fraction of the time, and with none of the accompanying mosquitoes.


Fifty-one minutes had now gone by. During that time, I was keeping an eye on its neighbor, who looked like this when I arrived:


Thirty-seven minutes in:


At forty-five minutes, its wings suddenly popped open:


And five minutes later, it flew away, leaving its exuviae still clinging to the leaf:


I didn’t feel the need to hang around for another hour to see the first one through to this point. Not far away, I found another that was still perched atop its exuviae but had finished getting “colored in”:


Today was evidently the day for these to emerge; there were numerous others along a short stretch of the brook. Here’s one more:


I’m not sure exactly what these are, beyond “some kind of clubtail” (Gomphidae). I think identifying these to species often requires a close look at the tip of the abdomen, and this may or may not cut it:


Edit: Ben Coulter and Dave Small concur that these are Southern Pygmy Clubtails (Lanthus vernalis).

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Another denizen of my lawn

I often write about the diversity of invertebrates that dwell in our unkempt yard, from the leafminers that colonized the first wildflower that popped up in the middle of it to the three dozen species that emerged from a shovelful of sod last spring. But we’ve also tallied 126 species of birds, mammals, reptiles, and amphibians in our yard and adjacent woods since we’ve lived here. One that has figured prominently in recent weeks is this porcupine:


Last fall I often heard it mumbling contentedly to itself as it grazed in the lawn outside my office window, but this was generally at dusk and it wasn’t usually around when Julia and I were outside. Over the winter we could regularly see it up in its favorite hemlock tree at the edge of our backyard, slowly dismantling it, and only sneaking into our yard at night to prune our raspberry canes. But lately it has been waddling through our yard on a daily basis, munching on the vegetation, completely unconcerned about our presence. It spends as little time as possible standing up, instead flopping down with its face buried in whatever it’s eating.


The other day we watched it for a while as it slowly worked its way toward the strawberry patch where we were sitting, and when it started to munch on a strawberry plant, Julia actually pushed its face away and it didn’t feel like that was anything worth raising its quills about. It just turned slightly and went back to munching on dandelion leaves.

So yesterday morning when I headed out the front door to do some yard work and saw the porcupine there, I decided it was time for a little photo session.


I’m sorry to say that what looks like its left eye in the above photo is actually a bloated tick. There’s one below its right eye too:


We don’t have any deer ticks in our yard, but for a few weeks in the spring there is a fair amount of dog ticks. They’re easy to spot when they venture onto our pant legs, and we hand-feed them all to our chickens.

In the next few shots the porcupine is enjoying some dandelion greens, which seem to be among its favorite menu items from our yard.


After the first few photos, which were taken with my 105mm macro lens (the one that happened to be on my camera when I grabbed it), I switched to the 18-55mm so I could get closer to the porcupine and not have so much grass in the way. In the next few shots it lumbered within about a foot of my face, and I had to keep backing up.


It contemplated this white violet for a moment, but ultimately decided to spare it.


It seems to prefer eating forbs, but I got one photo that clearly shows it biting off a blade of grass:


I think it’s pretty adorable when it uses its front paws to hold the plant it’s munching on.


This last couple of shots was taken as it began to waddle back down to the woods, pausing to bite the head off a dandelion along the way.


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Life in a Pinch of Duckweed

Five years ago, in June 2014, I was conducting a natural resource inventory for the Maine Coast Heritage Trust on a property in Perry, Maine (just across Passamaquoddy Bay from New Brunswick), when I came across this interesting little wetland:


The low area surrounded by a fringe of speckled alders (Alnus incana) consisted of an unstable Sphagnum mat covered with buckbean (Menyanthes trifoliata) and hoary sedge (Carex canescens).


Buckbean isn’t a plant I see very often, and I think this was the first time I got to see its frilly white flowers.


Part of my job was to make a map of the natural communities on the property, fitting all of the vegetation types I found into Maine’s natural community classification*. This wetland turned out to be a pretty good match for what they called the “Low Sedge – Buckbean Fen Lawn.” This is an uncommon community, and I never saw anything else like it in my three years of conducting inventories for MCHT, so when I returned at the end of August I made a point of revisiting the wetland to get a complete list of the plant species there. I even took a pinch of duckweed to key it out under my microscope back at home—if I hadn’t been paying special attention to this little wetland, I probably would have just scribbled down “Lemna sp.,” if I had even noticed the duckweed.

It turned out to be good old Lemna minor, the common duckweed. As I was examining the sample under magnification a few days later to make this determination, I was excited to discover that there were fly larvae feeding inside the tiny thalli (leaves, more or less). One is visible near the middle of this photo:


A closer look:


Other thalli contained puparia:


Surprisingly, there are several different insects that feed inside duckweeds, the smallest vascular plants. One of them is a shore fly (Ephydridae) named Lemnaphila scotlandae, after Minnie B. Scotland, who discovered it in the course of studying insects associated with duckweed in Ithaca, NY, throughout the 1930s**. The only other miner Scotland studied was a weevil, Tanysphyrus lemnae, but two other shore flies have also been found mining duckweeds in North America: Hydrellia personata, another apparent duckweed specialist, and H. griseola, which mostly mines in grasses but sometimes turns up in other plants.

The puparia I found were about 1.75 to 2 mm long, much too large for Lemnaphila scotlandae (~1.3 mm) and much too small for Hydrellia griseola (over 2.5 mm). They were within the right range for H. personata, but that species had only been found from Iowa to the West Coast. So I kept an eye on my vial of duckweed to see what would emerge.

In this photo taken a few days later, you can see a fully-formed fly almost ready to pop out of its puparium:


Between September 5 and October 2, nine of these little shore flies appeared:


Here I encountered an all too familiar problem: the insects I had reared belonged to a group that no one in North America studies. I sent them off to Canada with a batch of agromyzid flies, and Owen Lonsdale kindly attempted to run them through the most recent key to North American shore flies (published in 1971), but he didn’t reach a satisfying conclusion. So he passed them along to Tadeusz (Tadek) Zatwarnicki in Poland, who identified them as Hydrellia albilabris, a species known from many European countries but never found elsewhere until now. Whether H. albilabris is a recent arrival in Maine or has been a Holarctic species all along is anybody’s guess; there just hasn’t been much attention paid to these little flies.

Our paper documenting this discovery was just published today***. Why this took five years is another story, and not one that’s necessarily worth telling. So many bugs, so little time!

* Gawler, Susan and Andrew Cutko. 2010. Natural Landscapes of Maine: A Guide to Natural Communities and Ecosystems. Maine Natural Areas Program, Augusta, Maine.

** Scotland, Minnie B. 1940. Review and summary of studies of insects associated with Lemna minor. Journal of the New York Entomological Society 48(4): 319–333.

*** Eiseman, Charles S. and Tadeusz Zatwarnicki. 2019. First Nearctic record of Hydrellia albilabris (Meigen) (Diptera: Ephydridae), a leafminer of duckweed (Araceae: Lemnoideae), with comments on related species. Proceedings of the Entomological Society of Washington 121(2): 160–167.


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