Monthly Mystery #22: Bunchberry Squiggles

Last week I was back in Maine to finish up work on the natural resource inventories I’ve been conducting there.  On Tuesday, some reddish lines radiating from bunchberry (Cornus canadensis Chamaepericlymenum canadense) leaf bases caught my eye.

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The first set of keys I completed for my book on leafminers was for the order Cornales, which includes bunchberry along with other dogwoods, tupelo, hydrangeas, and mock oranges. So I have a good sense of what mines there are to be found on these plants, and when I saw these red marks, I was mildly curious what they were, but I knew they couldn’t be leaf mines, and since I had a lot to get done, I resisted the temptation to investigate them.

On Thursday, I was working at another site when I came across a bunchberry patch where practically every leaf of every plant had these red lines. Although I had a lot to get done that day too, I couldn’t ignore something this conspicuous and abundant, so I got down on my knees and started trying to figure out what they were. To my surprise, some of the red areas clearly contained narrow, squiggly lines that looked like they had to be leaf mines.

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I picked the plant in the above photo and held it up to the light.

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I could just make out little grains of frass (excrement) within the trails, confirming that they were leaf mines. However, there didn’t seem to be any larvae inside. This made sense in a way, since I imagined the red discoloration was something that developed after the mines were abandoned, but the mines were so narrow that it seemed like the larvae couldn’t possibly be done feeding. I wondered if the larvae of this species were initially leafminers, later exiting the mines to feed in some other way. I collected a good number of leaves, hoping that maybe one contained a dead larva whose DNA could be analyzed.

Conveniently for comparison, this same patch of bunchberry had examples of the leaf mines known to exist on this host. The only species that makes an entirely linear mine is a fly, Phytomyza agromyzina (Agromyzidae). Its mines are substantially wider, and rather than emanating from the leaf base, they start somewhere in the middle, almost always bumping into the tip at some point.

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The above plant, in addition to two fly mines and three mines of the mystery miner, has a very young mine of Antispila freemani (Heliozelidae) (take a look at the edge of the leaf at the left side of the photo.) This moth makes blotch mines that typically start at the leaf edge, widening from there. The photo below shows a somewhat more advanced one:

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The completed mine, as with the related Antispila cornifoliella, has an oval hole snipped out as a result of the larva constructing its pupal case.

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You can see from these examples that I wasn’t kidding about the red mines being on every leaf. Below is a presumed adult A. freemani that I found exploring a bunchberry leaf in Massachusetts last June. It looks pretty much the same as the A. cornifoliella adults I reared from roughleaf dogwood in Iowa.

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In the photo below, the whitish area in the lower left leaf was made by a larva of Caloptilia cornusella (Gracillariidae), which abandoned this blotch mine to roll up the lower right leaf.

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After feeding inside this leaf roll, the caterpillar returned to the original leaf to spin its cocoon on the underside, which caused the leaf to buckle a bit.

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Looking more closely, we can see that the pupa has already been thrust from the cocoon, allowing the adult moth to emerge.

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I reared an adult of this species two years ago from alternate-leaved dogwood (Cornus/Swida alternifolia) collected in Vermont:

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Another Caloptilia species feeds on bunchberry and has similar habits. At least one of the three dogwood-feeding Coleophora species (Coleophoridae) mines in bunchberry leaves, but Coleophora species produce unique frass-free blotch mines by feeding from a portable case attached to the outside of the leaf. These little red mines clearly correspond with none of the abovementioned insects.

As I was putting this post together, I realized that the backlit shot doesn’t show the frass very well, so I took more photos of the same leaves with my macro lens. It turns out that there are larvae inside the mines—all of them.

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In fact, in the full-resolution version of the above photo, I can make out three larvae, but the one toward the left edge is by far the largest. Here is the clearest photo I managed to get of one of these tiny larvae:

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Both the larvae and the mines remind me of the early portions of some Antispila mines, for example those on Virginia creeper. So my best guess is that these are mines of a previously undocumented Antispila species–not an outlandish idea, since cryptic and as yet unnamed Antispila species have recently been discovered on Virginia creeper, grape, and hydrangea–but I guess we’ll just have to wait and see…

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Virginia Creeper Miners

A year ago today, I was finishing up several weeks of fighting my way through horrible thickets of sweet pepperbush and greenbrier in southeastern Massachusetts, where I was visiting pre-established plots to identify plants for the UMass CAPS project. I had saved the most hard-to-access plot for last: getting there involved about two hours of trudging along mucky ATV trails and bushwhacking through the aforementioned horrible thickets. Probably there was a cloud of deer flies surrounding my head the whole time too, but that part of the ordeal has faded from my memory. When I had finished doing what I was there to do and was on my way back out, a leaf mine on a Virginia creeper vine along one of the ATV trails caught my eye.

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If you look closely, you will see that this mine started with a meandering linear portion (to the right), ending in the conspicuous blotch. When finished feeding, the larva cut out an oval piece from the leaf to use as its pupal case. This identifies its maker as a species of Antispila (Heliozelidae), which is a genus I have previously discussed here. The species is probably Antispila ampelopsifoliella, but as discussed in this recent paper, there is at least one undescribed species hiding under this name, and more work is needed to sort out the various Antispilas on Virginia creeper and grape. So I spent a little time looking for some mines with larvae still inside. I don’t think I found any, but soon afterward I found them in my own front yard, and the adults that emerged three months ago looked like this:
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Anyway, standing there after my exhausting day of fieldwork, I soon became distracted by the discovery of a second mine type, made by the only other leafminer known to feed on Virginia creeper: Phyllocnistis ampelopsiella (Gracillariidae). Don Davis had recently told me that there are no specimens of this species in the Smithsonian National Museum, and that he was very interested in seeing some to compare with the two (or more?) Phyllocnistis species on grape. This was the first time I had found a mine of this species, so I started flipping over leaves to look for more. The larva forms a very contorted mine that is only visible on the lower leaf surface.

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In the above example, the whitish mine (with some brownish patches) covers the whole area below the midrib, as well as the area to the right of the hole above the midrib. The slight wrinkle in the leaf margin at the bottom of the frame is where the larva has spun a cocoon inside the mine. When backlit, the mine is invisible except for a thin, continuous line of excrement, as shown in the detail below.

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From these mines I managed to rear adult moths, which emerged a few weeks later and looked like this:

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But the point of all this is that while I was standing there scrutinizing all the Virginia creeper leaves for mines of these two moths, I found a third type of mine that was something else entirely.

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The mines were more or less linear, with short, seemingly featureless yellow larvae mining side by side in pairs. Together, the larvae produced distinctive double lines of excrement, as seen in this backlit example:

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The larvae looked like they might be agromyzid flies, but none of these are known to mine in members of the grape family, and the mines were not at all like agromyzid mines. I wasn’t at all sure what order of insect I was looking at. When the larvae started to pop out of the mines two days later…

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…I could see clearly that they weren’t flies or moths, but I still wasn’t sure whether these legless blobs would turn out to be beetles or maybe some kind of strange parasitoid wasp I had never encountered before. They burrowed into the jar of soil I offered them, and I checked it obsessively to see what would come out. On August 31, I was shocked to find this roly-poly little weevil in the jar:

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I posted photos to BugGuide.net, and eight minutes later Vassili Belov suggested that the weevil was a species of Orchestomerus. Doing a little reading, I learned that this genus includes three described species in the United States. One is found throughout the eastern US, another is known only from Arizona, and a third was described from a single specimen collected in Brownsville, Texas and apparently nothing had been published about it in the 100+ years since then. The first two have been collected as adults on grape foliage, and the third had not been associated with a host plant. Nothing was known of the immature stages of any species in the genus, but given the association with the grape family, it seemed that Vassili was on the right track. It also appeared, based on the original descriptions of these three beetles, that I had the Texas species. I ended up with three adult specimens, which I sent to weevil specialist Bob Anderson. He agreed that the weevils were the Texas species, Orchestomerus wickhami. In addition to Texas, he had specimens from Louisiana and (just like mine) Plymouth County, Massachusetts. A curious distribution, to be sure.

So I wrote up my discovery and submitted it to the Coleopterists Bulletin, which published my short paper in March*. I was excited to document not just a new host association, but the first natural history observations for any member of this genus (which also includes a number of tropical species). However, the story doesn’t end there. Soon after my paper was published, Bob informed me that my find had inspired him to conduct a review of the genus–in part, I think, to get a better sense of the geographic distribution of the species. He dissected a male O. wickhami he had collected and compared it with one of mine, and he reported that “they are different, very different.” He has since determined conclusively that my Virginia creeper weevils belong to a separate, undescribed species, which means that the title of my first peer-reviewed publication is a lie. On the plus side, I found a “new” species and, unlike most of the other “new” species I have found, a taxonomist is actually working on describing it. I will report back when the Orchestomerus revision is published and this beetle has a new name!

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* Eiseman, Charles S. 2014. Orchestomerus wickhami Dietz (Coleoptera: Curculionidae: Ceutorhynchinae) reared from leaf mines in Virginia Creeper (Parthenocissus Planch., Vitaceae). The Coleopterists Bulletin 68(1):158-160.

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Monthly Mystery #21: Double Cocoons

On pages 219-220 of Tracks & Sign of Insects, I described the cocoon of Neurobathra strigifinitella (Gracillariidae) according to the account of Heinrich and DeGryse (1915)*. I then included a photo of a mysterious cocoon found on the underside of a sugar maple leaf in Nashville, Tennessee, which seemed to be somewhat similar but lacked the pearl-like globules that decorate the cocoon of N. strigifinitella.

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Well, last weekend I collected some N. strigifinitella larvae mining oak leaves on Nantucket, and last night I got to see my first cocoon of this species. It is now clear that the mystery cocoon is nothing like it, nor is it like the cocoon of any other gracillariid moth I have reared.

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This one is less than 8 mm long, not 14 mm as stated by Heinrich and DeGryse. Noah and I found four examples of the mystery cocoons on that sugar maple, ranging from 8 to 12 mm across.

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The example below was overlapping a Phyllonorycter (Gracillariidae) leaf mine and had a thrips running around inside its outer wall. Neither had anything to do with the maker of the cocoon. Curiously, there doesn’t seem to be any entrance hole in the cocoon, and it seems like the thrips may have gotten trapped inside it after chewing its way out of the leaf mine.

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I haven’t found any of these cocoons since that day six years ago (July 4, 2008), but I sure would like to know what they are. It may or may not have been significant that they were on sugar maple leaves. Unfortunately the larvae aren’t visible enough in the photos to even say to what order they belong. I’m starting to wonder whether they might be some obscure type of neuropteran (lacewing or something similar), since those tend to make some variety of double cocoon (e.g this dustywing).

* Heinrich, Carl and J. J. DeGryse. 1915. On Acrocercops strigifinitella Clemens. Proceedings of the Entomological Society of Washington 17:6-23.

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Nantucket Moths

As you have probably guessed, my lack of posts lately has been due not to my having run out of things to write about (I don’t think this could ever happen to someone who spends any time observing insects), but to my being too busy with fieldwork and taking care of my ever-growing menagerie of insects and spiders I’m trying to raise. I’ve just finished a weekend of leafminer surveys on Nantucket, and I found myself with a few minutes of spare time this evening to go through the ~500 photos I’ve just taken here. Since this is the last day of National Moth Week, I thought I’d share with you a few of the striking moths I’ve bumped into incidentally while wandering around and scouring leaves for evidence of tiny insects. I haven’t had a chance to look many of these up yet, so I don’t have much to say about them other than that they’re nice to look at.

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This is some kind of clearwing moth (Sesiidae) that does a very good job of looking like some kind of vespid wasp. It seems to be something in the tribe Paranthrenini.

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This one was perched on a leaf in a flooded ditch along a cranberry bog. Suspecting that it was one of the crambid moths with aquatic larvae, I just took a quick look at some of those and it looks like a good match for Elophila icciusalis, which has been given the common name of Pondside Pyralid (which is unfortunate, since it’s a crambid rather than a pyralid). I believe Elophila is one of the genera with larvae that make portable cases of leaf pieces, sort of like those of caddisfly larvae.

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I saw two of these silvery, orange-bordered moths today in dry, grassy areas. I assume it’s one of the many grass-feeding crambids. [Added 7/28/14: I'm now thinking it's Argyria nummulalis, which is indeed one of the grass-feeding crambids.]

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This one is a pyralid, I think in the subfamily Phycitinae, and possibly a species of Acrobasis, of which the larvae live in cornucopias of their own poop.

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This is a slug caterpillar moth (Limacodidae), and appears to be the Spiny Oak-Slug Moth (Euclea delphinii). There was certainly plenty of oak around.

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There were three rows of these flat, overlapping eggs on a single woolly bulrush (Scirpus cyperinus) leaf in a marsh. I think for the moment I won’t hazard a guess as to what type of moth they might belong to.

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This is my new favorite thing. It is a small caterpillar that has aligned itself with the midrib of a scrub oak (Quercus ilicifolia) leaf and spun an intricate silken net over a section of the leaf, beneath which it has been eating little patches of leaf tissue to either side of the midrib. It has carefully decorated the strands of the net with tiny pellets of excrement. A few minutes after I picked this leaf, my mind suddenly flashed to a page in Dave Wagner’s field guide to eastern caterpillars. I believe this is a very young Melsheimer’s Sack-bearer Moth (Mimallonidae: Cicinnus melsheimeri), which later will construct a portable case of leaf pieces, in which it will overwinter before transforming into an adult moth. If I’m right, this is a state-listed Threatened species, which is at its northern range limit here. I’ll find out when I get home to my books tomorrow. In the meantime, here are some interesting photos of a sack-bearer my friend Eric LoPresti found in the Bahamas, which I believe is something in the same genus.

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Monthly Mystery #20: Mudball on a String

Two weeks ago, as I began exploring the first of seven properties where I am conducting natural resource inventories this year for the Maine Coast Heritage Trust, I noticed a little ball of mud hanging from a goldenrod leaf. I was intrigued, but resisted the temptation to investigate it: I had lots of ground to cover, and I didn’t want to get distracted by minutia before I had accomplished anything. After I encountered a third one, however, I gave in and took some photos, then collected it.

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The only one of these I remember seeing before was the one pictured on page 45 of Tracks & Sign of Insects…, which Noah photographed as we were wandering along a river in Pennsylvania. The paragraph accompanying that photo discusses how McCook (1884)* referred to the spider that makes this egg sac as Micaria limnicunae, and how it is unclear to what species that name refers. Platnick and Shadab (1988)**, in revising the genus Micaria (Gnaphosidae), listed this as an uncertain name:

The name M. limnicunae was applied only to egg sacs and spiderlings from Illinois, and no specimens identified by McCook can now be located in the collections of the Philadelphia Academy of Natural Sciences (Dr. James Newlin, in litt.); as Banks (1893) indicated, McCook’s description is “worthless.”

The spider may not even be a Micaria; McCook himself thought it might actually belong to the genus Herpyllus, which includes the eastern parson spider (H. ecclesiasticus):

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Unfortunately, as far as I can tell, every known gnaphosid (ground spider) egg sac is an unadorned, disk-shaped object. Possibly some spiderlings will emerge from the egg sac I collected and shed some light on this mystery, but so far I have never succeeded in raising any kind of spider from egg to adult.

Here’s another observation that may or may not be relevant: Two years ago I collected this sand-covered egg sac, which was one of many found under some snake boards (big pieces of plywood lying on the ground) on Nantucket:

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Some spiderlings emerged, but none lived to be more than about 1.5 mm long.

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I would have had no clue what to call them, but Mandy Howe recognized them as liocranid sac spiders, probably in the genus Agroeca. Fortunately, Andrew McKenna-Foster has done extensive spider surveys on the island, and he told me that Agroeca is the only liocranid he has caught there. He has identified two species, A. pratensis and A. ornata; the former seems to be more common there.

It is well known that some European Agroeca species construct pendulous, dirt- or mud-covered egg sacs, but I haven’t found any references to American species doing this. Is McCook’s description of Micaria limnicunae so “worthless” that it might actually refer to an Agroeca? I haven’t checked, and I don’t know enough about spider identification to be able to judge, but I would be interested to hear an arachnologist’s take on this.

* McCook, H. C.  1884. A spider that makes a spherical mud-daub cocoon. Proceedings of the Academy of Natural Sciences of Philadelphia 36:151-153.

** Platnick, N. I. and M. U. Shadab. 1988. A revision of the American spiders of the genus Micaria (Araneae, Gnaphosidae). American Museum Novitates 2916:1-64.

 

 

 

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Another Mystery Solved, Sort Of

At the beginning of this month, I reported having found these tied leaves on smooth aster (Symphyotrichum laeve) plants in my backyard.

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On May 27, I had put three samples in jars on my desk to see what might emerge.  On June 9, this caterpillar appeared in one of the jars, apparently because the leaves had deteriorated to the point where they were no longer edible. I put it in a clean jar with a fresh sprig from the same host plant.

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On June 23, I returned home from a week in Maine to find this dead ichneumon wasp in one of the other two jars. I suspect, based on its color pattern, that it is something in the subfamily Pimplinae*.

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Meanwhile, the caterpillar had pupated between a leaf and the side of the jar, without so much as a nibble on the replacement leaves. On June 27, as I was heading out the door for the weekend, I happened to notice a moth fluttering around in that jar. I quickly took a few photos of it and then stuck it in the fridge until I got home this evening. After a few minutes browsing through superfamily Gelechioidea on BugGuide.net, and then a few Google searches for “orange palps,” I arrived at a definite match: Dichomeris ochripalpella (Gelechiidae), whose known hosts include heart-leaved aster (Symphyotrichum cordifolium), hoary aster (Machaeranthera canescens), and Canada goldenrod (Solidago canadesis). Having identified it to species and having determined that I hadn’t discovered anything new, I was able to spare the life of a beautiful moth and have a chance to get some photos of it on its host plant in my yard instead of on a plain white background.

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Apparently I never took a photo of the pupa before the moth emerged, but here’s what it looked like after it was thrust from the silken chamber between the leaf and the glass so that the moth could come out.

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The only problem with all this is that the identity of the Iowa goldenrod leaftier pictured here remains a mystery.  I had wondered when I first found the leaf ties in my backyard whether the two were really the same, since in the Iowa examples there was a silk-lined tube that ran through the whole series of leaves, and this didn’t seem to be the case with the ones in my backyard. Once I saw what the Massachusetts larva looked like, I knew I had something completely different. So I’ll have to keep watching for those goldenrod tubes… it may be that they can only be found in the fall.

* I suspected wrong. Bob Carlson informed me that the wasp belongs to the subfamily Campopleginae, noting that “the only campoplegine that has been reared from this host is Meloboris marginata (Provancher), but this is definitely not that and appears to be Campoplex or Sinophorus.”

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Another Mystery Host Plant

Last week Owen Lonsdale gave me a first batch of identifications from the big box of agromyzid fly specimens I sent him a few months ago. Unfortunately, of the ten species represented, he was only able to put species names on three (of these, it appears that one is a new host record, one a new state record, and one a new US record). Four were only identifiable to genus because the specimens were all females. The remaining three were new species.

Two of the three new ones are from New England, and their host plants are species I know well. The third emerged last spring from leaf mines I collected in Iowa the previous September. The host plant was growing in a small patch at the base of a bur oak in the middle of a huge lawn in a park. There were only basal leaves (no flowers or fruits to help identify it).

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At the time I had the impression that it was a waterleaf (Hydrophyllum), but on looking at the photos later, I was pretty sure it wasn’t. This shot of the leaf mine gives a better view of the leaf margin and vestiture.

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When I asked John Pearson, who had initially agreed with my thought that it was a waterleaf, to take another look, he suggested that it was a buttercup, and maybe early buttercup (Ranunculus fascicularis). That looks like a plausible match to me, but I’d like to be as sure as possible before I go reporting that as the host plant of this new species. So if anyone out there has other suggestions, or has experience with R. fascicularis and can confirm John’s suggestion, please let me know.

The fly itself, incidentally, looks like this:

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Externally, it looks awfully similar to many other Phytomyza species. The identification is all about the male genitalia–which Owen says place it in the Phytomyza aquilegiae group. This group is associated with the buttercup family (Ranunculaceae), so John’s suggestion is certainly on the right track.

Not all of the new species that have been emerging from my collected leaf mines are so cryptic. I brought these moths to Dave Wagner a few months ago, and upon taking one quick look, he said he thought they represented a new genus. He saved one for DNA analysis and sent the rest off to Don Davis at the Smithsonian, to join the hundreds of other unnamed gracillariid species awaiting description.

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