The Yard List(s), Part 8

You may recall that back in early April I said that this year I would be listing not just the leafminers and edible plants I find in my yard, but also the sawfly larvae. So ever since I spotted the Monoctenus female laying eggs in the arborvitae hedge along the road, I’ve been checking every couple of days or so for her offspring munching away on the needles. No luck so far, but on today’s trip to the hedge I did see my first sawfly larva of the year—not on the arborvitae but on a black cherry sapling growing right next to it. Julia was able to guess what I’d found right away, with no other information than that I had found a sawfly larva, combined with my level of excitement at having found it:


Yes, Sterictiphora, eating its characteristic “curious winding slit” into the leaf, as first described by Harrison Dyar back in 1897. I wrote about my first encounter with one of these in June 2013, and in May 2015 I shared some more examples, including photos of the adult S. serotina I reared from that first larva. This one in my yard may or may not be S. serotina; there are six Sterictiphora species in North America, and at least four of them feed on Prunus species (though one is known only from the western US). Sterictiphora prunivora feeds on both Prunus and AmelanchierS. sericea had no known hosts until I reared one from Amelanchier last year*; and S. transversa (with the curious distribution of Alaska, Alberta, and Maryland) still has not been associated with any plant.

Here’s a closer view of today’s larva (the field of view here is 11 mm wide):


On a neighboring branch of the same black cherry sapling was a female Orchestes pallicornis. Just yesterday I wrote about having seen this species in my yard, and said that “Soon, females will be inserting eggs along the midribs of leaves, and the larvae will form linear mines extending toward the leaf tips.” Well, there she was, chewing her third oviposition hole in the midrib of a leaf at the tip of the branch:


I don’t think I’ve ever actually witnessed this before, so naturally I spent a while watching her, in between bouts of admiring the Sterictiphora‘s sinusoidal splendor. Two minutes after I first noticed her, she turned around and began inserting an egg in her most recent hole.


Wow, I didn’t think I had sat there for that long, but according to the time stamps on the photos, it was 36 minutes later that I took this picture of her excavating a fourth hole:


If you look closely you can see the dark spot where her little black schnoz is buried in the midrib. And here she is inserting an egg in that same hole:


While I sat there entranced by these two tiny bugs doing their thing, I suddenly noticed that this cherry sapling had several bark mines on it:


Since the mines are on a black cherry, we know that they were made by a larva of the moth Marmara serotinella (Gracillariidae)—miner #16 for this year’s list. If you read yesterday’s post, you’ll remember that I have a white ash branch in a vase on my kitchen counter being mined by a larva of M. fraxinella. Yesterday I wrote that “Over the past ten months or so, the larva mined 22 cm toward the tip of the branch, then turned around and mined 20.5 cm back down.” Amazingly, as of right now (~27 hours later), it has lengthened the downward mine to 23 cm and turned around once again, mining 5 cm back up the branch. Clearly Marmara larvae pick up the pace as they reach maturity.

And finally, since yesterday’s post, I was able to add one more species to the “plants I have eaten” list:

55. Strawberry (Rosaceae: Fragaria × ananassa) – fruit

The strawberries in the open-air gardens are in flower right now, but we have a few in our hoop house that got going early. I would have gotten to add strawberry to the list a few days ago, but some little rodent devoured the first two fruits just as they were developing a blush of red. I then placed inverted jars over the three ripest remaining fruits, and that provided adequate protection from the buck-toothed bandits to allow them to turn solid red.

Oh, and on my way back to the house from the photo session, I spotted another Sterictiphora larva on a different black cherry sapling. Can’t get enough of these little cuties.


* Eiseman, Charles S. and David R. Smith. 2020. New sawfly (Hymenoptera: Argidae, Tenthredinidae) host records from northeastern North America. Proceedings of the Entomological Society of Washington 122(2): 299–307.

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The Yard List(s), Part 7

Last night I finished revising and updating the Lepidoptera chapter for the second edition of Leafminers of North America, and when I got to the end I was reminded that some species of Leucania (like the ill-fated one I wrote about earlier this month) start out life mining in blades of grass. Yes, even big ol’ noctuids can be leafminers. There’s no escaping them.

Anyway, it’s been nearly a week since my last post, and in the meantime several more miners have appeared in my yard.

#12: Marmara fraxinella (Gracillariidae). On May 22, Julia and I were cutting some saplings from the edges of the yard for use in our new tomato infrastructure, and at the top of a 15-foot white ash (Oleaceae: Fraxinus americana) sapling was this fresh-looking stem mine:


It can often be difficult to trace a Marmara mine from beginning to end, but because this mine was made recently and because this species mines throughout its development in the outermost layer of bark, following this one was a piece of cake.

The transparent shell of the egg that was deposited early last summer is visible at one end…


…and the yellowish larva, still feeding away in the bark, is visible at the other end.


It’s admittedly harder to see than the larva of a leafminer, but it’s there all right, in the upper left corner of the above photo. This is actually within 2 cm of the eggshell, but on the other side of the branch. Over the past ten months or so, the larva mined 22 cm toward the tip of the branch, then turned around and mined 20.5 cm back down. The branch is currently sitting in a vase on the kitchen counter where I can keep an eye on it. I’ve never tried to rear this species before, but it is one that, like Marmara viburnella, spins its cocoon under a bark flap excised at the end of the mine, so I don’t have to worry about the larva wandering off or drowning in the water in the vase.

The next three species came in the form of adult beetles, and since I wasn’t carrying a camera when I saw them, I’ll illustrate them with photos from past years.

#13: Orchestes pallicornis (Curculionidae). On May 23 I spotted this weevil nibbling on a leaf of black cherry (Rosaceae: Prunus serotina) at the edge of the yard.


Like Dibolia borealis, this flea weevil has a single generation per year, with larvae feeding in spring or early summer and with adults overwintering. Soon, females will be inserting eggs along the midribs of leaves, and the larvae will form linear mines extending toward the leaf tips.


Older larvae form blotch mines and then spin circular cocoons in which to pupate. Here is a communal mine with three cocoons inside:


#14: Chalepus walshii (Chrysomelidae). Yesterday morning when I went to pick some pokeweed shoots for lunch, I found an adult of this beetle perched at the tip of a blade of reed canary grass (Poaceae: Phalaris arundinacea).


A few inches below it was one of the characteristic rectangular feeding patches I illustrated here. This is another species that has a single generation and overwinters as an adult, but C. walshii larvae can be found later in the season than those of D. borealis and O. pallicornis. Reed canary grass wasn’t known to be a larval host of C. walshii until I found some mines in my yard last July and reared a couple of adults from them.


This is immediately recognizable as a Chalepus mine because of the characteristic brown egg covering near the tip of the leaf, as well as the dark brown frass expelled from the leaf margin.

#15: Brachys aerosus (Buprestidae). Yesterday afternoon I spotted this species nibbling on the edge of a red oak (Fagaceae: Quercus rubra) leaf.


Once again, this is a leaf-mining beetle with a single generation per year, but Brachys species overwinter as larvae within their mines rather than as adults. They pupate once the weather warms up, and the adults emerge about a month later. Eggs are laid in summer, but the larvae take their time, and they can still be found feeding in late October, as in this example (the larva is at far right):


In contrast, the Aulagromyza cornigera larva that appeared on May 18 had already exited its mine when I checked on May 22:


On May 23, I went to check on the Caloptilia serotinella larva I’d found two days earlier. It had crossed the midrib, but otherwise hadn’t made much progress.


Actually, looking at the photo now, I can see that the larva crossed back over the midrib and exited through a hole in the epidermis just below the midrib, to the left of the frass line. So it turns out this species will sometimes make an entirely linear mine, rather than the linear-blotch mines I usually see.

In any case, as I arrived at that black cherry sapling, the wind happened to blow a neighboring leaf in such a way that I noticed a similar mine that was only visible from the lower surface.


I believe this is another C. serotinella mine. Some Caloptilia species aren’t particular about which side of the leaf they mine.

The next day, silk spun by that larva within the blotch portion of the mine had caused the mine to buckle and become “tentiform.”


And once again, now that I look at the photo on the big screen, I can see the larva had already exited at this point—the hole is at the far left end. But not having noticed this yet, I went back one more time yesterday to check on the mine’s progress, and the leaf had now completely folded over, concealing the blotch.


Having seen these exit holes, I had to dash out into my yard just now—flushing a gorgeous male indigo bunting from the dandelions by the front door—and verify that yes, the larvae have now formed neighboring leaves into conical shelters in which to complete their feeding, as Caloptilia larvae should.


I think we’re all caught up now, in terms of leafminer happenings in my yard… Meanwhile, I’ve partaken of another four edible plants from the yard since last time:

51. Common milkweed (Apocynaceae: Asclepias syriaca) – shoots
52. Riverbank grape (Vitaceae: Vitis riparia) – leaves
53. Wild leek (Amaryllidaceae: Allium tricoccum) – leaves
54. Pokeweed (Phytolaccaceae: Phytolacca americana) – shoots

Just in case anyone reading these posts is inspired to go out and try the plants I’ve been listing: please do some research first! The shoots of both milkweed and pokeweed, for instance, require boiling for seven minutes or so before eating, or you’ll be sorry. I’d never tried pokeweed before, but it turns out to be delicious, as advertised—somewhat similar to asparagus. Milkweed is also quite good, and don’t worry, there is plenty left for the monarchs, and the milkweed tussock moths, and the large and small milkweed bugs, and the milkweed long-horned beetles, and the milkweed weevils, and the milkweed leaf-mining flies—all of which are equally deserving of our affection and it drives me nuts when people want to kill or remove any non-monarch organism they find on their milkweed plants. If you simply refrain from mowing your lawn, you will soon have more than enough milkweed to suit everybody’s needs. We got enough from weeding a few strawberry and asparagus patches yesterday to provide the main vegetable for last night’s stir fry and this morning’s omelet, and new shoots keep popping up faster than we can pick them.

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The Yard List(s), Part 6

First of all, check out this lovely rhodora (Ericaceae: Rhododendron canadense):


This is a shrub of bogs and other wet habitats that I don’t get to see very often—or didn’t until now. I picked this one up last fall at a local native plant nursery, and it’s now happily blooming in the ever-shrinking lawn next to my house.

Second, I have some updates on the “leafminers of my yard” front. As you may recall, three days ago I found this Aulagromyza cornigera mine on one of our honeyberry bushes:


As of today there still seems to be just the one mine, but that larva has made some good progress:


When I took these photos, there was a braconid wasp lurking on a nearby leaf, so this larva may be in trouble…

Meanwhile, as of today leafminer species #10 and #11 have appeared in the yard. One was the miner I was anticipating finding next, and I’ve been checking the blackberry plants (Rosaceae: Rubus allegheniensis) every day for it, but as it turned out I wasn’t even looking for it today when I noticed two of the brownish blotch mines. I couldn’t find the larva at first, but when I came back with a camera and grabbed the plant to tilt it to a good angle for photographing one of the mines, I almost squished the larva between my thumb and forefinger.


At right in the above photo is the characteristic blotch mine of a casebearer moth (Coleophoridae: Coleophora), with a round entrance hole on the lower surface through which the larva extended the front of its body to feed without leaving its portable house. At left is the larva in its case, pretending to be a bud. Here’s a closer look:


The case is made of silk and pieces of blackberry leaf, and the larva has been adding to it periodically as it grows. The whitish nubbin at the top is the larva’s tiny initial case, which it constructed sometime last year.

In this backlit view of the mine, you can see that the mine is full-depth (all the tissue between the two epidermises has been eaten), and that it is totally clean: the larva keeps its tail end in the case while mining, and periodically backs up to the tip of the case when it needs to get rid of some frass.


Because it’s feeding on blackberry, we know this casebearer is Coleophora cretaticostella. As it happens, I have reared this species just once, from a larva collected about 50 feet away from today’s larva, six years ago to the day. In fact, my photos of the first larva were taken six years to the minute before I took these photos. The adult emerged at the end of June:


I found leafminer #11 at the opposite corner of the yard, on a black cherry (Rosaceae: Prunus serotina) sapling that started out as a fox scat full of cherry pits deposited in the lawn, also about six years ago. This is another mine I happened to spot out of the corner of my eye as I was walking by.


Today’s finds are a good illustration of the diversity in leaf mines. The Coleophora mine is a full-depth blotch with no frass inside; this second one is an epidermal linear mine with a continuous line of frass down the middle. In an epidermal mine, the larva is feeding within the thin epidermal layer just below the leaf cuticle, drinking the cells’ liquid contents but not consuming any tissue—which is why in the backlit view there is no difference in transparency between the mine and the surrounding tissue. Mines like this are characteristic of the moth family Gracillariidae. I have found no mention in the literature of gracillariid mines on cherry that start out with a long linear portion. However, I have found these mines many times before, on both black cherry and choke cherry (P. virginiana). When complete, the mines are blotchy at the end, as in this example on choke cherry:


Here’s another example, in which the blotch portion has caused the leaf to curl, partly concealing it:


Terry Harrison has reared adults from mines like this in Illinois; they are the “Parornix sp. 2″ pictured here.

The weird thing is, after several years of failed attempts, I managed to rear adults from several different collections of these mines in July 2018, and all of them turned out to be Caloptilia serotinella rather than Parornix. Unfortunately they emerged while I was on a road trip and I didn’t get to photograph them alive, but here’s an adult of the same species that I found on my wall in December 2018—presumably brought in with firewood:


The leaf mine of Caloptilia serotinella has not been described in the literature, but when C. R. Ely described the species in 1910, he noted that the mature larva folds the tip of the leaf over to form a hollow tetrahedron. The vast majority of Caloptilia species similarly abandon leafmining as older larvae and construct a leaf roll of some sort in which to finish feeding.

…And finally, this week has brought the number of plant species I’ve eaten from my yard up to 50:

48. Red clover (Fabaceae: Trifolium pratense) – leaves
49. White clover (Fabaceae: Trifolium repens) – leaves
50. Wild sarsaparilla (Araliaceae: Aralia nudicaulis) – shoots

I’d never tried any of these before this spring. It turns out that young clover leaves are high in protein and perfectly palatable if cooked for a few minutes. And tender shoots of wild sarsaparilla are pretty tasty; as Arthur Haines notes, eating a lot of them raw produces a mild irritation in the back of the mouth, but a little cooking takes care of this. This morning we had some in an omelet, along with winter cress, tower mustard, stinging nettle, curly dock, clover, and other goodies—all collected on the way to the garden, to which I never made it because I had all the food I needed before I got there.

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The Yard List(s), Part 5

Back on May 5, spring was cooking along; flowers were opening on the Virginia bluebells that I had completely forgotten we had planted among the ostrich ferns under the old apple tree last year.


But a few days later we had a setback, in the form of some snow that fell on the night of the 8th, into the morning of the 9th.


The snow melted away, but then we had a couple of frosts, which presented even more of a threat to the flowers and tender young leaves that had just opened up. The last one (I’ve decided it was the last one) was on the morning of the 14th. Amazingly, the flowers made it through all this pretty much unscathed, which was especially surprising with the peaches.


We tucked the asparagus patch in with blankets each night, which turned out to be worthwhile, since the two stalks we missed on the first night got frostbitten and turned to mush. Otherwise, the main casualties were the sensitive and interrupted ferns in the woods; some maple leaves will end up a little disfigured but have now resumed expanding. Spring is now back in full swing, and everywhere are new leaves presenting blank canvases for leafminers and other leaf-feeding insects to make their marks.

One plant I’ve been watching closely is the honeyberry (Caprifoliaceae: Lonicera caerulea), because this and other honeysuckles are the hosts for Aulagromyza cornigera (Agromyzidae), one of the first leafminers to show up apart from those that overwinter as larvae. This afternoon, there it was: a lone A. cornigera larva etching its characteristic white trail with discrete black frass grains.


In just a few days, the mine will be complete…


…and the larva will pop out of the leaf, drop to the ground, and form a puparium…


…not emerging as an adult until next spring.


So that brings the “leafminers in my yard” total to nine so far this spring. It is the first one to arise from an egg laid this year, not counting the Chrysoesthia sexguttella mines that are now becoming abundant on the lambsquarters in the hoop house. Those larvae are the progeny of adults that emerged in early April, but I didn’t see an adult of that species outside the hoop house until last week, so they are more than a month ahead of schedule.

In my first post about the leafminer yard list, I said there were larvae of both Argyresthia thuiella (Argyresthiidae) and Coleotechnites thujaella (Gelechiidae) overwintering in the arborvitae hedge along the road. I said this with confidence because there are mines all over the trees; although the mines of the two species are indistinguishable, I have seen adults of both on that hedge, and I have reared C. thujaella from some of the mines. The truth is, though, I have never found a definite mine of A. thuiella there or anywhere else, and I’ve been watching this spring to see if I can spot some larvae. Although the mines of the two species are identical, they can be identified when larvae are present because A. thuiella larvae are green while those of C. thujaella are brown. Today I finally noticed some fresh, whitish mining extending out from the old, brown mines that were made last fall.


(The difference was more apparent to my eyes than to my camera’s sensor.) But alas, every mine I photographed with bright backlighting had a brown larva inside. The green larvae of A. thuiella remain elusive.


For a consolation prize, I found this sawfly laying eggs in some of the needles.


I surmised based on the host plant that she belongs to the genus Monoctenus (Diprionidae), which Dave Smith confirmed. There are at least three Monoctenus species in eastern North America, but there is no key that can be used to identify them. Dave says, “The genus needs study.  The one in the Northeast is usually called M. suffusus,  I’ve called the one I get around here [northern Virginia] M. melliceps.  I’ll have to wait till I get back to the Museum [the Smithsonian, which of course is closed due to COVID-19] to check. One would think this might be an easy project, but it will take a lot of dissecting saws [ovipositors] and male genitalia.” For what it’s worth, M. suffusus is the only name that has been linked to arborvitae (Thuja occidentalis); this species has also been reported to feed on eastern redcedar (Juniperus virginiana). Monoctenus melliceps (which also occurs in Massachusetts) has not been associated with any host, and M. fulvus (a midwestern species) has only been reported from eastern redcedar. I’ve never seen a Monoctenus larva, but I’ll be watching for them now. My only previous experience with Monoctenus was having a male emerge from an arrowwood plant Julia and I had dug up, potted, and bagged in a failed attempt to rear adults of the stem-mining moth now known as Marmara viburnella.

And on the foraging front, the last couple of weeks have added several more plants from the yard to our menu:

36. Rhubarb (Polygonaceae: Rheum × hybridum) – petioles
37. Asparagus (Asparagaceae: Asparagus officinalis) – shoots
38. Watercress (Brassicaceae: Nasturtium officinale) – leaves
39. Bull thistle (Asteraceae: Cirsium vulgare) – roots
40. Lesser burdock (Asteraceae: Arctium minus) – roots
41. Sea kale (Brassicaceae: Crambe maritima) – leaves
42. Maple-leaved goosefoot (Amaranthaceae: Chenopodiastrum simplex) – leaves
43. White sweet clover (Fabaceae: Melilotus albus) – leaves
44. English plantain (Plantaginaceae: Plantago lanceolata) – leaves
45. Jewelweed (Balsaminaceae: Impatiens capensis) – leaves
46. Groundnut (Fabaceae: Apios americana) – tubers
47. Ostrich fern (Onocleaceae: Matteuccia struthiopteris) – fiddleheads

I’ve only tried groundnut a couple of times in the past because it’s usually hard to dig up and there is no guarantee that the tubers will be big enough to make it worth the effort. However, we’ve allowed the plants to spread into our main strawberry patch over the past few years, with the result that we got several meals’ worth simply by weeding the strawberries this week. They’re delicious, with a flavor somehow halfway between peanut and potato.


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52 Wasp Pickup

Back on April 7, Noah stopped by to get some eggs and some seeds for his vegetable garden. Just as he arrived and Julia was walking up to meet him, she spotted a caterpillar with a tiny wasp on it. I dashed into the house to grab my camera, and the wasp was still hanging around when I returned.


Amazingly enough, the wasp still clung to the caterpillar after it was picked up and placed on the driveway for a better view.


The caterpillar proceeded to go running across the driveway at a steady clip, so it is somewhat miraculous that I was able to get a few sharp close-ups of the 1.5-mm eulophid wasp.


Now, I was assuming the wasp was inserting eggs in the caterpillar, but as I reviewed the photos on my camera after the wasp finally flew away, I realized she had actually been laying eggs on the surface.


Twenty-six of them, to be precise. (One of them is obscured in the photo below, but see the following photos if you want to check my math.)


So naturally I scooped up the caterpillar once more and put it in a jar so I could chronicle the development of the wasp’s progeny. To do this, I’d need to keep the caterpillar fed. All I knew was it was some kind of owlet moth (Noctuidae), but Sam Jaffe of The Caterpillar Lab recognized it as a middle instar Leucania species. He said if I could rear it through another instar or two it might be possible to narrow down the species possibilities. I wasn’t sure how much time this caterpillar had left, but I gathered from the Wagner et al. guide to owlet caterpillars that Leucania species are generalists on trees and shrubs, none of which had leafed out yet, so I collected an assortment of leaves from around the yard and hoped for the best. The caterpillar became pretty inactive and didn’t seem to have much of an appetite, but it ultimately munched a bit on some dewberry and strawberry leaves.

The next day, the caterpillar had contracted, and I thought maybe it was getting ready to molt. Would it be able to shed the eggs before they hatched?


The eggs had already darkened noticeably.


The following day, the caterpillar had stretched back out, without having molted.


With the caterpillar sitting still and with its skin unwrinkled, I was able to get a photo clearly showing all 26 eggs.


On April 12, nothing much had changed.


On April 15, the eggs had begun to split open.


On April 18, the caterpillar had become very active again. The white larvae were now mostly emerged from their darker eggshells, but had not moved away from them. I presume their mouthparts were now latched onto the caterpillar, so it was understandable that it had become a bit restless.


The next morning, I was surprised to find the caterpillar dead, with 26 fuzzy white cocoons spun on a nearby strawberry leaf.


But these were braconid cocoons! The poor caterpillar already had 26 braconid larvae living inside it when that eulophid wasp showed up to lay another 26 eggs on it. The eulophid larvae still clung to the caterpillar’s corpse, which was now riddled with dark spots where the braconid larvae had emerged.


I kept the caterpillar to see if the eulophids would be able to keep developing now that their host was dead. They had grown considerably by the next day (April 20).


On April 21, none had grown further and several of them had begun to shrivel up. Mold had also started to grow on the caterpillar.


On April 24, a few were still hanging onto life, but still weren’t growing any.


A few days later, the caterpillar was consumed with mold, and all hope was lost for these few lingering larvae. I believe these eulophids belonged to the genus Euplectrus, the larvae of which continue to feed in a tight cluster throughout their development, turning a striking bluish color when mature*:


When finished feeding, Euplectrus larvae disperse and spin a mass of loose cocoons—which could easily be mistaken for mold growth—beneath the remains of their host caterpillar.


Anyway, on May 4, all 26 of the braconid wasps emerged from the cocoons that had appeared on April 19. They were very zippy but I managed to get a few decent photos.


They belong to the subfamily Microgastrinae, and I’m guessing the genus Cotesia. Someday, when the staff at the Canadian National Collection of Insects are allowed to go back to work, I’ll send them to José Fernández-Triana and he can tell us exactly what they are. Assuming they have a name.

I suppose now is a good time to follow up on this post from eight years ago that included a pile of Cotesia cocoons with a sprinkling of Eulophus pupae on top—evidently the result of a second wasp ovipositing on an already parasitized caterpillar before it was too late for both sets of offspring to complete their development.

I collected this in September 2012, and the wasps emerged the following spring—a dozen or so Eulophus between April 28 and May 11…


…and about 20 Cotesia between May 6 and 23.


From one of the Cotesia cocoons, a hyperparasitoid emerged—an ichneumonid in the genus Itoplectis.


Whether the mother of the Itoplectis laid an egg in the Cotesia cocoon or had to locate a Cotesia larva within the host caterpillar, I don’t know. Either way, these were two unlucky caterpillars.

* Added 5/6/2020: The Caterpillar Lab has been rearing similarly parasitized Leucania pseudargyria / ursula caterpillars this spring, and these particular Euplectrus larvae are evidently pale yellowish throughout their development, turning a little pinkish when mature.


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The Yard List(s), Part 4

May has started off with a string of beautiful, sunny days, and more new birds have been announcing their arrival each day. On the 1st it was the blue-headed vireo; on the 2nd a ruby-throated hummingbird joined the myriad bees, wasps, and flies buzzing around the plum trees that had just burst into bloom, while a blue-gray gnatcatcher wheezed from the trees around the edges of the yard; yesterday the morning started off with the song of a black-throated green warbler, followed before long by ovenbird, common yellowthroat, black-and-white warbler, chestnut-sided warbler, gray catbird, eastern towhee, and barn swallow; and this morning a rose-breasted grosbeak and Baltimore oriole have already joined the chorus (those two always seem to arrive together).

Amid all these arrivals, the season’s eighth leafminer species has made its presence known in my yard: plantain flea beetle (Chrysomelidae: Dibolia borealis). As with the Chrysoesthia sexguttella that are still swarming inside the hoop house, it is the adults rather than the leaf-mining larvae that are now appearing. Unlike those moths, though, these beetles are not newly emerging from pupae; they have been hunkered down as adults since early last summer. I woke up this morning thinking how odd it is that the tiny beetles that are now nibbling the plantain leaves in the lawn were already adults last July when we bought the little fuzzy day-old chicks that are now full-grown hens, laying enough eggs every day to feed me and Julia as well as several neighbors.


After nibbling on plantain leaves for a few weeks, the beetles will begin laying eggs on them, and in June the trails of the larvae mining inside them will be obvious.


When full-grown, the bright yellow-orange larvae will exit their mines and burrow into the ground to pupate, emerging as adults in July.


The new adults may nibble on plantain leaves for a little while, but soon they will go into hiding until the following spring.

Dibolia borealis is among that small minority of native North American species that have become more common and widespread since Europeans arrived here. Over five hundred years ago, they would have fed only on the native Plantago species, which are spotty in their distribution. But they have expanded their diet to include the European P. major, which is now ubiquitous in lawns and other disturbed areas. In Helen Reed’s study of this species at Cornell University nearly a century ago*, she stated that both adults and larvae of D. borealis appear to feed exclusively on P. major, although she found that captive larvae would mine into leaves of another European import, P. lanceolata, when given no other choice. I did find a single mine on P. lanceolata in my yard three years ago, but it is clear that this is not a preferred host.


Meanwhile I, adaptable creature that I am, have so far eaten 35 different plant species in my yard this spring. The latest additions:

31. Tall blue lettuce (Asteraceae: Lactuca biennis) – leaves
32. Carrot / Queen Anne’s lace (Apiaceae: Daucus carota) – roots
33. Virginia waterleaf (Hydrophyllaceae: Hydrophyllum virginianum) – leaves
34. Tower mustard (Brassicaceae: Turritis glabra) – leaves, flowers
35. Shepherd’s purse (Brassicaceae: Capsella bursa-pastoris) – leaves, flowers, fruits

Asparagus, you’re next!

* Reed, Helen. 1927. Some observations on the leaf-mining flea-beetle Dibolia borealis Chevrolat. Annals of the Entomological Society of America 20(4): 540–549.

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Sawfly Surprise

As I’ve mentioned a few times before, I’m starting to work on a hostplant-based guide to sawfly larvae that will be arranged similarly to my leafminer guide. In addition to reviewing the existing sawfly literature, I’ve been sporadically collecting larvae to rear, and I plan to do a lot more of that this year. Since the hosts are known for only about a quarter of the North American sawfly species, raising them to adults will often be necessary to figure out what species I’ve found. For the past few years, I’ve been keeping an eye out for sawfly larvae to collect while surveying for galls and leaf mines on Nantucket. Here’s a striking one I collected there on September 5, munching on the edge of a leaf of beaked hazelnut (Betulaceae: Corylus cornuta):


Five days later, it had molted to its final instar:


And by September 13, it had spun this cocoon among the crumpled paper at the bottom of the rearing container:


On April 1, something emerged from the cocoon—but instead of an adult sawfly, it was 44 beautiful little green wasps:


Although I’m used to them being more nondescript, I eventually recognized these as tetrastichine eulophids. Evidently the larvae are internal parasitoids, since there was no external evidence that anything was amiss with the sawfly larva. Lacking a reared adult sawfly, I have to rely on existing sawfly hostplant records to determine the identity of the larva, but it seems like there’s a pretty good chance it was Arge pectoralis (Argidae), a species more commonly found on birch but also recorded from hazelnut and alder (all plants in the birch family). Tetrastichus trisulcatus is the only tetrastichine eulophid that has been reported as parasitizing this or any other Arge species, and it is apparently a sawfly specialist, but sawfly parasitoids are of course more poorly known than sawflies themselves, so the wasps that came swarming out of that cocoon may or may not have been T. trisulcatus.

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