A Hidden Masterpiece

Last December, Jennifer Kleinrichert sent me this photo of a polka-dotted larva (prepupa) surrounded by an elaborate silken structure, wondering if I knew what it was:

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My response:

I’m afraid I don’t know this one… I’ve seen a photo of something similar once before; see the third one on this page. It would be interesting to know if this larva ends up spinning a similar dense, white cocoon. The polka-dots on your larva remind me a little bit of some pyraloid moths… can you tell me anything else about the context?  Looks like it was under a plywood board?  If you don’t mind, I’d love to post this as a mystery on my blog.

 
She replied that she and her husband had been changing some pictures in a bulletin board, and upon opening the door found the larva in between the two frames. In the photo below, the larva’s creation is visible on the horizontal board directly below the photo of a viceroy.

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I decided to hold off on posting the mystery here, because in January Julia and I happened to be visiting her parents in Ohio, just a half-hour drive from the bulletin board, and I figured I might as well take a crack at raising the larva to an adult. Jennifer and her husband Steve met us at the bulletin board and removed the panel for us. The larva was still in the same position within its gauzy double fence, which was about 6 cm across.

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We gently removed the larva and put it in a sandwich box with a  folded-up paper towel.

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I kept it in the refrigerator until March 1. After that, I took a peek at it every day, and although I didn’t actually see it move much, it seemed to be in a different position every time I looked. I expected it to pupate soon after it was exposed to warmer temperatures, but it wasn’t until nearly two months later, on April 23, when I found the larva suspended in some webbing in a fold of the paper towel where I hadn’t seen it venture before.

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Another week passed, and finally, on May 1, it shed its skin and pupated.

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I didn’t want to disturb it too much then, but I was able to get a better shot of the larval and pupal exuviae on May 27, when the adult moth at last emerged.

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My guess that it was some sort of pyraloid moth turned out to be correct. Specifically, it was a dogbane saucrobotys (Crambidae: Saucrobotys futilalis). I don’t think I had seen an adult before (at least, I had never been moved to photograph one), but the larvae were conspicuous in the dogbane patch by our mailbox last September.
 
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I never would have guessed that the larvae leave their messy feeding webs to spin such intricate structures for hibernating and pupating.

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Bean Borer

Last August, Julia noticed a few holes in some string beans in the garden.

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One of holes had droppings pouring out of it, and we could see someone fuzzy inside.

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I opened this tunnel up for a better look at its inhabitant.

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A quick look in a field guide told me what this was going to turn into, and I generally focus my rearing efforts on unknowns, but I decided to make an exception. After munching on beans for another week, it shed its fuzzy skin to reveal a fuzzy brown chrysalis.

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In the spring, it emerged as a gray hairstreak (Lycaenidae: Strymon melinus) as expected. It obligingly posed on a dandelion before fluttering away.

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We’re more than happy to sacrifice a few string beans to have these around.

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Birch Munchers, Large and Small

The woods behind our house were logged not long before we moved here, and as a result there are lots of black birch (Betula lenta) saplings around. Yesterday on my morning walk I spotted this amazing caterpillar eagerly devouring the leaves on one of these saplings:
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Caterpillars of this species get to be well over 10 cm long. In the spring they emerge as cecropia moths (Saturniidae: Hyalophora cecropia), which some sources say are the largest moths in North America. Others say the black witch (Erebidae: Ascalapha odorata) is larger, which may be true for adults, but the caterpillars of that species are only up to 7 cm long. Here’s the only adult cecropia I’ve photographed, from over a decade ago:

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Just a little farther down the trail, I noticed some black birch leaves containing larvae of Nepticulidae, the family that includes the smallest moths in the world. This one leaf has 14 larvae in it:

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If you look closely at the above photo, you can see the bright yellow larvae at the ends of the mines. Here is a close-up of the largest mine:

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I believe these are Stigmella corylifoliella or something else in the S. betulicola species group. Here is a moth I reared last year from a similar larva:

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This two-millimeter moth would fit on one of the red knobs on the cecropia caterpillar’s back.

Looking at some other mined black birch leaves, I saw that not all of the Stigmella larvae were yellow. Note the nearly colorless one at the bottom of this photo:

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Here’s a leaf with only the pale larvae, some of their mines nearly complete:

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The pale larvae pretty consistently fill the first part of their mines with frass particles carefully placed in closely spaced, zigzagging arcs, then transition to making a narrow central frass line toward the end of the mine.

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Erik van Nieukerken has determined that there are at least six different Stigmella species forming linear mines on birches in North America, and I believe this is one that doesn’t have a name yet. I reared some adults this spring, but I haven’t gotten that far in my photo sorting yet.

I saw some other leafminers and leaftiers on black birch as I continued on my walk, but I didn’t feel moved to photograph these. But then I saw this leaf, and couldn’t resist taking a closer look:

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Flipping the leaf over to look at the underside, I saw what was responsible for the little whitish patches. See the elongate object near the tip of the leaf?

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Here’s a closer look:

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It’s the portable case of a casebearer moth (Coleophoridae: Coleophora), made from a piece cut out from a leaf. In this backlit shot, you can see the larva inside, its head right at the mouth of the case:

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A casebearer feeds by attaching the mouth of its case to the underside of a leaf, chewing a hole in the lower epidermis, and mining into the leaf by extending the front of its body out from the case. Well, that’s how older larvae feed; the youngest larvae feed as regular leafminers, their bodies entirely within the mine. The mine is then cut out from the leaf to form the portable case. In the case above, you can see that the larva left the very tips of the leaf serrations unmined. The presence of leaf serrations tells us that the case was cut from the edge of a leaf—in fact, it came from the base of this very leaf.

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The photo above shows the underside of the leaf, and you can see that there is something projecting from the left edge of the missing leaf piece. This is a smaller case that the larva abandoned when it mined into the leaf to create the case that it is currently wearing. And where did that case come from? I surveyed the various holes in the leaf (most of which were not made by this larva) in search of one the right size and shape. I knew I had found the right one when I saw that it, too, had a smaller abandoned case attached to it!

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This one was just a millimeter long. To the right of it, you can see a tiny mine the larva made while living in this case; the entrance hole is in the lower right corner. The origin of this original case appears to be a nearby hole that is visible in this zoomed-out view (which shows several more mines made by the young larva before cutting its third case):

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Five Coleophora species are known to mine birch leaves, but taking this one’s habits into account I can rule some of these out. I suspect it is C. lentella, which happens to be the only one of the five that has been reported from black birch (and its name is a reference to this host, Betula lenta). It might turn out to be C. comptoniella, though; if so, it will make yet another, much larger case after overwintering. Of the five birch feeders, I have so far only reared C. serratella:

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I found another larva of the same type on another leaf of the same sapling. This one was wandering in search of a new feeding site:

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I’m going to attempt to rear these, but I’ll be more likely to succeed if I can find more in the spring.

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Adapting to New Menu Options, Part 2

One of the reasons certain nonnative plants come to dominate the landscape is that they are released from the specialized insects and pathogens that keep them in check in their native range. So I’m always interested to see what insects are able to make use of these plants. I’ve often noticed little nibbles like this on Japanese barberry (Berberis thunbergii)…

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…but had never actually spotted anything feeding on the leaves until one autumn day when I stopped to investigate some particularly fresh-looking nibbles. This “window feeding” (leaving one epidermis intact) turns out to be the work of early instars of an inchworm, which starts eating all the way through the leaves as it grows larger.

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The above photo was taken on September 28. Here is the same caterpillar on October 2…

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…and October 8:

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The caterpillar burrowed into soil not long after this, emerging as an adult in March after I took its jar out of the fridge.

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Its patterned wings became good camouflage when it came to rest on the fallen white pine in my yard:

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This native moth is known as the barberry geometer (Geometridae: Coryphista meadii), and barberries are its only known host plants. Its original host is presumed to be American barberry (Berberis canadensis), but this plant does not occur in the Northeast. So like Stigmella rhamnicola (but even more dramatically), this moth has expanded its range because of the introduction of a nonnative plant. Sorry to say the little nibbles made by the caterpillars aren’t enough to keep the barberry from taking over places where the deer are selectively eating all the other understory plants.

Last October I discovered that barberry geometers aren’t the only caterpillars feeding on leaves of Japanese barberry. Whereas the inchworms “window feed” from the lower leaf surface, I found these two caterpillars grazing in little patches on the upper leaf surfaces:

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These are the same two caterpillars a week later:

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Five days later, they looked much more similar to one another:

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Unfortunately I was unable to rear these to adults. I have found similar caterpillars feeding on Christmas fern (Polystichum acrostichoides) and wintergreen (Gaultheria procumbens) in the fall, so I think this is just a species that feeds on whatever is still green at the end of the year rather than any kind of barberry specialist. It’s some sort of owlet moth (Noctuidae); I had one of the wintergreen feeders emerge in June, but I haven’t figured out what it is yet and I’m nowhere near there in my photo sorting, so stay tuned…

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Moths From A Willow Leaf

Over the past few days, a break in fieldwork has given me a chance to start catching up on going through my photos from this year—I’m exactly five months behind at the moment. On March 19 I finally got to the end of a story that started with the Berkshire BioBlitz on June 19 of  the previous year. I had collected this leaf of silky willow (Salix sericea) in the hope of finding out which of the nine willow-feeding species of Phyllonorycter (Gracillariidae) was responsible for the leaf mine on it, since as far as I know there is no way to distinguish among the mines of these species (though a few can be ruled out based on geography).

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In my hurry to document as many species as possible in a short time, I didn’t investigate what had made the webbing and leaf fold next  to the mine. This nearly proved disastrous, since it turned out a caterpillar was hiding in the leaf flap, and by the next day it had consumed much of the leaf. Fortunately, it didn’t eat too much of the mined portion.

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I moved the caterpillar to a separate vial with fresh willow leaves. I don’t usually collect non-micro moth caterpillars to rear, but when they show up on leaves I’ve already collected I figure I might as well.

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On June 28, the adult leafminer emerged, revealing itself to be Phyllonorycter salicifoliella, and leaving its pupal skin protruding from the mine.

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The externally feeding caterpillar developed much more slowly, and I had to keep collecting new willow leaves to feed it. Here it is on July 6 with an old willow leaf that has gone yellow:

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On July 29 it was looking pretty different:

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The last photo I took of it was on August 4…

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…but I noted in my journal that it turned pink and burrowed into soil on August 12. As it happens, I had tried to rear this same species eleven years earlier (from a caterpillar feeding on black cherry), so I have a photo to illustrate just how pink it was when ready to pupate:

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Nothing stirred in the jar for the rest of the year. I put it in the fridge over the winter, taking it back out on March 1. Almost three weeks later, an adult confused woodgrain (Noctuidae: Morrisonia confusa) appeared in the jar. Having no further use for it, I let it out to see if it could find others of its kind. Here it is resting on a fallen white pine at the edge of my yard:

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Giving Wasps Their Due

I often see pie charts like this one suggesting that about a quarter of all insect species are beetles. Suspiciously, other sources (e.g. here) say beetles represent about a quarter of all animal species, and Wikipedia goes so far as to say beetles constitute “almost 25% of all known life-forms”! (they may have meant to say “animal life forms”, but a pie chart here does show beetles representing about 20% of all organisms). The first statement is probably closest to the truth, but I suspect that it is based on numbers of described (named) species, and I can’t help but wonder if this figure is a result of a disproportionate number of people studying beetles. I’ve lost track of how many undescribed moths, flies, and wasps I’ve found in just the past few years; the moths and flies belong to groups that are studied by just one or two people in North America, and the situation is even worse for parasitoid wasps and gall wasps: for most of the wasps I’ve reared, I can’t even find a specialist to examine them and determine whether they match any described species.

According to Wikipedia, there are about 400,000 described beetle (Coleoptera) species in the world, with estimates of total species ranging from 850,000 to 4 million. There are about 180,000 described moths and butterflies (Lepidoptera), over 150,000 wasps, ants, bees, and sawflies (Hymenoptera), and about 150,000 flies (Diptera). I haven’t seen an estimated total number for Lepidoptera, but there are said to be one to three million Hymenoptera species and about a million Diptera species.

It seems like every insect has a set of more or less host-specific wasps that parasitize it. Even parasitoid wasps have wasps that parasitize them. So it’s hard for me to believe that there aren’t more wasp species than anything else. I looked around for estimated numbers for the major parasitoid groups, and found that the family Braconidae has roughly 12,000 described species, with 50,000 being a “probably highly conservative” estimate of the total number in the world. The related family  Ichneumonidae has 24,281 described species  and “probably includes more than 100,000 species” total. According to BugGuide.net, in North America it is estimated that there are 3000 species in this family alone remaining to be discovered and/or named, the same as the estimate for the entire beetle order (there are currently about 25,000 named beetle species and 5000 ichneumonid species in North America). The superfamily Chalcidoidea has about 22,000 described species, with an estimated total of more than 500,000 according to BugGuide.

With a thousand or so described species, the subfamily Platygastrinae (Platygastridae) is a relatively small group of wasps. (The wasps themselves are small, at a millimeter or so long.) As far as is known, all of them parasitize gall midges (Cecidomyiidae). As of 2014, there were 6203 known species of gall midges, with the number of species still unknown being “inestimable”.* It seems to me that the true number of platygastrines is therefore likewise inestimable, and I suspect that Peter Neerup Buhl’s report on the eight sets of platygastrid specimens I sent him last year is representative of the current state of knowledge of this group. As I mentioned here, he identified one of the wasps as Metaclisis floridana and another as a Synopeasnot identifiable to species because it was a male, but possibly S. pubescens; neither M. floridana nor S. pubescens had ever been reared before. The remaining six were all species of Platygaster, a genus with about a hundred known species in North America. Of these, one keyed to P. baccharicola but its antennae were broken off and it couldn’t be identified with certainty; two were males and therefore unidentifiable; and the remaining three didn’t match any known species. Our paper describing them was published last month**, so I can now introduce them to you:

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Platygaster pruni is a parasitoid of Contarinia cerasiserotinae, which forms galls on black cherry (Prunus serotina) that look like this:

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The larvae of Contarinia cerasiserotinae pop out of their galls in late May, burrow into the ground, and emerge as adults the following spring.

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However, in my one attempt to rear this species (from galls collected in Leverett, Massachusetts), all that emerged the following spring were a male and female of Platygaster pruni and this as yet unidentified eulophid:

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The other two new species were reared from gall midges that are themselves likely undescribed. The host of the first has never been reared (adults are unknown), but its larvae are common in western Massachusetts. They form leaf spot galls on wild oats (Uvularia sessilifolia), which are sometimes already empty by late May…

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…but sometimes larvae are present as late as early July. The whitish larva is only visible on the lower leaf surface.

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The larvae of this species likewise exit their galls and burrow into the ground, presumably emerging as adults the following spring.

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The four females and two males of Platygaster uvulariae all emerged on May 18.

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The last species came from the same site on Nantucket where I found Megaselia nantucketensis and is likewise known from a single specimen. Its host midge develops in little blisters on grape leaves; the blisters project from both leaf surfaces and have a little central tuft on each side.

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The larvae exit their galls in the first half of August, once again burrowing into the ground and overwintering.

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I did manage to rear two adults of this species, but they were in poor shape when I discovered them on May 15.

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Ray Gagné confirmed that they belong to the genus Vitisiella, and probably a new species, but the genus needs to be revised before that can be said with certainty. A third midge emerged on June 5 and was in good shape when I found it, but it turned out to be an inquiline (not the gallmaker), Lasioptera vitis.

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The single female of Platygaster vitisiellae emerged the same day.

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Hard to estimate how many Platygaster species there might be when every specimen I rear is either unidentifiable or a new species!

* Shortly after I posted this, Jason Dombroskie alerted me to this brand new paper (published just three days ago), which used DNA barcoding to estimate insect diversity in Canada. The estimate for gall midges is 16,000 out of 94,000 species, which they extrapolate to 1.8 million cecidomyiid species out of ten million insect species worldwide. Addressing the very point I was making at the beginning of this post, they state that if their estimates are accurate, “the global species count for this fly family may exceed the combined total for all 142 beetle families.”

** Buhl, Peter N. and Charles S. Eiseman. 2016. Three new reared species of Platygaster (Hymenoptera, Platygastroidea: Platygastridae) from the United States. International Journal of Environmental Studies, DOI: 10.1080/00207233.2016.120132

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Introducing Brachys howdeni

The state flower of Massachusetts is mayflower, which no longer seems an appropriate name since it blooms in April these days (I even saw some flowers in March this year). Another name for this plant is trailing arbutus, and I’ve always liked its Latin name, Epigaea repens (Ericaceae), because both the genus and species describe it well: Epigaea means “on the earth,” and repens means “creeping.” Its evergreen leaves form mats on the ground in dry, sunny areas, and its fragrant, white to pink flowers are visited by all sorts of insects in the spring.

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Mining bee (Andrenidae: Andrena)

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Greater bee fly (Bombyliidae: Bombylius major)

On January 7, 2012, I went for a walk with some friends on a ridge that happens to be just up the hill from where Julia and I now live. That was the winter that I started working on my leafminer book, and a year earlier I would probably have passed off the brown edging on this trailing arbutus leaf as something unrelated to insect feeding:

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However, since I had leafminers on the brain, I picked the leaf and held it up to the sky, and sure enough, I could see frass and a larva inside (the larva is at the lower left in the photo below).

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I was far enough along in my book project that I was pretty sure no insect was known to mine Epigaea leaves, so I kept an eye out for more of these mines over the next few months and collected them from several different locations.

At the same time, I was systematically going through all the known groups of leaf-mining insects and tracking down literature on their natural history. One day I went to the UMass science library to peruse (among other things) some papers by Henry Hespenheide on leaf-mining beetles*. I think that was the first time I had come across his name, so that evening I was surprised to see it pop up in that annoying “ticker” column on my Facebook newsfeed, which I normally ignore. He was discussing Philly cheesesteaks with a mutual acquaintance. I suppose my eye was conditioned to spot a newly familiar name in my peripheral vision, in the same way I was beginning to spot leaf mines where I never would have noticed them before. Anyway, I was glad to know how to reach Henry if any beetle questions should arise.

On April 16, the first adult emerged from one of the trailing arbutus leaf mines, and it was a buprestid (jewel beetle) in the genus Brachys.

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Brachys species are mostly associated with oaks, although some have been reared from leaf mines on various other trees. Since leaf-mining buprestids are among Henry’s specialties, I showed him this photo to see what he thought of it. He replied: “I know about this species and have a couple of specimens that Henry Howden reared decades ago. I would be happy to describe it if you have a nice series, say 5-10 specimens. . . Brachys is a VERY difficult genus with many cryptic species, but this one seems distinct enough to describe without revising the genus.”

Since then, I’ve provided Henry with around 20 specimens reared from trailing arbutus. I also collected some aborted mines and reared two different parasitoid wasps (Eulophidae) from them: three females of the purple-headed Neochrysocharis diastatae

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…and a tiny male of the genus Pnigalio, which is itself in serious need of revision:

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Over the past few years Henry has studied my Brachys adults from trailing arbutus and various other hosts, plus countless specimens others have reared or collected all over North America. Last year he described three new species from New Mexico, Texas, and Mexico**, and last month our paper describing the trailing arbutus miner was published***. Henry named it Brachys howdeni, since Henry Howden was the first to rear this species. It is very similar to B. aerosus, and the number of other species hiding under that name is yet to be determined. Stay tuned…

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* Hespenheide, Henry A. 1992. A review of the genus Tachygonus (Coleoptera: Curculionidae) north of Mexico. Proceedings of the Entomological Society of Washington 94(1):1-11.

* Hespenheide, Henry A. 2003. A reconsideration of Pachyschelus schwarzi Kerremans and a review of American Pachyschelus north of México (Coleoptera: Buprestidae). The Coleopterists Bulletin 57(4):459-468.

** Hespenheide, Henry A. 2015. Striking new species of Brachys Dejean, 1833 (Coleoptera: Buprestidae) from New Mexico, Texas, and Mexico. The Coleopterists Bulletin 69(2):221-224.

*** Hespenheide, Henry A. and Charles S. Eiseman. 2016. A new species of Brachys Dejean, 1833 (Coleoptera: Buprestidae) from the eastern United States using an unusual host. The Coleopterists Bulletin 70(2):335-340.

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