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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Life and Death on Mt. Greylock

This past weekend I attended my third Berkshire BioBlitz. At my first one in 2011, I barely left the parking lot at the summit of Mt. Greylock and photographed 166 different species of insects and arachnids. This time, Julia and I actually made it into the woods, taking about four hours to complete the 0.7-mile Rounds Rock trail loop. Our list this time was not as impressive, mainly because we kept encountering things that were more interesting than just tallying as many species as we could. One of the first things Julia spotted was a leafminer that I’m confident is new to science, so we had to spend a while dealing with that. Not long after we resumed our slow walk, she flipped over an oak leaf to get a better look at a sawfly larva that was munching the edge, and she called me over to see an ichneumon wasp that was stalking up to it on the underside of the leaf. The wasp had almost reached the larva when I got there:

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The larva continued to munch away obliviously as the wasp inserted her ovipositor just behind its head.

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When she was done, she backed away but continued to watch the larva for a while, approaching it again and closely inspecting it, then wandered off.

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You may have noticed the yellow object stuck to the larva’s thorax.

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My best guess is that this is the egg of another ichneumon wasp in the subfamily Tryphoninae. These wasps have stalked eggs that they attach externally to their host larvae. There is a photo of an egg on a preserved specimen here; I’ve never seen a photo of a fresh one. With larvae of two different ichneumon wasps feeding on its innards, it’s probably safe to say this sawfly isn’t going to make it to adulthood.

We plodded along for about 40 minutes until Julia spotted something else that compelled me to spend 15 minutes sitting and photographing it: a treehopper emerging from its last nymphal skin. I got to it just as it was getting its abdomen free, but was able to watch the lengthening of its wings and pronotum.

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We didn’t hang around to see it become fully colored. There were a few adult treehoppers like the one below in the immediate vicinity, but the molting one seemed to be a different species.

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We had made it just a few steps down the trail when a colony of aphids caught my eye.

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There are always other insects to be found in association with aphids, and before long I noticed this syrphid fly larva resting on a stem:

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Then I turned around and saw a wasp with its ovipositor stuck in another syrphid larva on the underside of a leaf.

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As with the icheumonid parasitizing the sawfly larva, this wasp was poking the syrphid larva’s “neck.” I’m thinking the wasp is a figitid, maybe in the subfamily Aspiceratinae. Both of the observations of this rarely seen wasp group on BugGuide show females ovipositing in syrphid larvae. This one wandered off for a bit, then returned to the larva.

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She climbed onto the larva again, this time ovipositing into its abdomen.

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Meanwhile, Julia saw the first syrphid larva grab an aphid, and I turned around to see it holding its prey out from the stem, devouring it.

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I’m not sure what that yellow blob is on the aphid’s antenna. I initially thought it was a mite, but it doesn’t seem to be. Anyway, we pulled ourselves away from these two dramatic scenes and made our way to the top of Rounds Rock, an open area with lots of lowbush blueberry. I stopped to investigate what appeared to be a tentiform mine on a blueberry leaf, but it it turned out to be a midge gall… with a torymid wasp ovipositing in it.

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Here’s a shot of the underside of one of these galls—a simple fold at the edge of the leaf.

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There are a number of midge galls like this on various plants, but it appears that none have been recorded previously on blueberry. I’ll see what I can do about rearing some.

A lot to see on a short trail loop—and in fact we hadn’t quite covered half of the 0.7 miles at that point.

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Connecticut BioBlitz

A month ago Dave Wagner got in touch with me and Julia, saying we were needed at the 2016 Connecticut State BioBlitz on June 3 and 4. He wanted to make sure leafminers were properly represented in this attempt to break the record for the most species ever recorded in a single 24-hour BioBlitz. The area to be surveyed was a five-mile radius around a school in East Hartford, an area that is mostly pavement but includes a few fragments of floodplain and upland forest. We took the challenge, and this past weekend we helped document a total of 2765 species, breaking the previous record of 2519 that was set in 2001. It was hard not to just start writing down every plant and bird we encountered, but we knew other people had these covered, so we focused on leafminers, gallmakers, and other poorly known insect groups.  We ended up contributing 133 species to the tally; our gall wasps, sawflies, and leaf-mining moths represented small fractions of the 197 Hymenoptera and 442 Lepidoptera recorded, but our gall midges and leaf-mining flies accounted for about a fifth of the 183 Diptera. Here are a few of the things we saw along the way:

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Friday afternoon we explored the woods by the Mt. St. Benedict Cemetery north of Hartford. We encountered many different kinds of sawfly larvae, most of which I couldn’t hope to identify, but I recognized the spiky oak feeder above as a species of Periclista, and a Google search for “black locust sawfly” quickly identified the one below as Nematus tibialis (both Tenthredinidae). We also found four different leafminers (two moths, one beetle, and one fly) on black locust.

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I was also able to recognize these black cherry feeders as Sterictiphora (Argidae), based on their distinctive feeding pattern, which I have written about before.

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The woods around the cemetery also yielded a walkingstick nymph (Diapheromeridae: Diapheromera femorata)…

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…a distinctively marked long-horned beetle (Cerambycidae: Strangalepta abbreviata)…

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…an unusual abundance of buffalo treehoppers (Membracidae: Ceresa)…

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…signs of leafcutter bees (Megachilidae: Megachile)…

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…a leaf mine of the apple flea weevil (Curculionidae: Orchestes pallicornis) on shadbush (Rosaceae: Amelanchier)…

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…and this tortricid, which seems to be Cydia nigricana—a new state record, but not a particularly exciting one, since it’s an introduced species.

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On the way back to the cemetery parking lot, we spotted some mines of Parectopa plantaginisella on fleabane (Erigeron), as well as some superficially similar blotch mines on the same plants which backlighting revealed to be the work of Nemorimyza posticata (Agromyzidae). This fly has not been recorded from Erigeron before, but the intricate feeding lines produced by the larvae are characteristic. I have reared adults from several other genera in the aster family that were not previously known to be hosts of N. posticata, so there is no reason to doubt that it uses fleabane as well.

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Back at the school, all the naturalists gathered in a big room and pored over their finds. Assorted galls, cocoons, and the like were sent my way, including these beautiful cocoons of Hypera rumicis (Curculionidae) on curly dock (Rumex acetosella).

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I took these home with me, and one of the weevils emerged yesterday:

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On Saturday morning we walked around the school for a little while, at one point finding leaf mines of seven different genera of agromyzid mines within a one-meter radius. There were also some lovely (albeit nonnative) snails…

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…and some equally attractive (but likewise nonnative) fourteen-spotted lady beetles (Coccinellidae: Propylea quatuordecimpunctata).

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From there we headed to the nearby Hockanum River Linear Trail, where one of the first things we found was a new host record for the leaf-mining beetle Mantura floridana (Chrysomelidae). I’m trying to rear them to confirm the record. In the first photo below you can see three of the bright yellow larvae clustered together inside a leaf; the second photo is a good example of the finely squiggly frass that is sometimes produced by leaf-mining flea beetle larvae.

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A little further down the trail we found mines of a Bucculatrix angustata larva (Bucculatricidae) in leaves of an aster (Symphyotrichum).

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The larva first made a long, narrow mine along the margin of the lower leaf, then moved to the upper leaf and made a broader mine. The larva can be seen clearly in this backlit shot of the same mine:

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Also along that trail, I found this caterpillar mummified by a species of Aleiodes (Braconidae). I probably could have identified the wasp to species using this guide to eastern caterpillar mummies, but never got around to it.

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Right at the end of the trail, Julia spotted bark mines of the elusive Viburnum Marmara. Another new state record, and this one for a native species—but of course the species doesn’t have a name yet.

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On our way back to the car, I managed decent shots (both with slightly blurry faces) of two striking little insects: Mathildana newmanella (Oecophoridae)…

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…and Metriorrhynchomiris dislocatus (Miridae).

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Not a bad day’s work.

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No, Not Leafcutter Bees

Okay, there have been six votes for leafcutter bees being the culprit for yesterday’s mystery sign. Dave Almquist was the only one to qualify his guess: “They look almost like partial cuts from leafcutter bees, assuming that the leaves are small enough for that.” I would agree with that: they do look almost like partial cuts from leafcutter bees (Megachilidae: Megachile), but there are a couple of subtle clues suggesting something else. (They are, in fact, a bit larger than the cuts a leafcutter bee would make, but I realize I didn’t provide anything for scale.)

Here are a few examples of interrupted leafcutter bee cuts, along with completed cuts where the bee removed a circular or oblong piece from the leaf.

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Notice how the pieces are cut all along the leaf margins, in no way focused on the midrib or the major veins. Also notice that the cutouts are made by cutting in one direction: none of the interrupted cuts shows any evidence of the bee starting an opposing cut, and the complete cuts never have a disjointed part in the middle where two cuts didn’t quite line up. In some cases the asymmetry of the cut makes it clear which way the bee was moving (for instance, clockwise in the one in the lower right corner of the second photo). Each of the following photos has another clear example of one of these lopsided, spiral cuts:

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Now take another look at the leaf I found yesterday:

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See how there are two counterclockwise cuts that start at the leaf margin and end at the midrib or a major vein? Each of these has a paired cut that was supposed to meet the first one from the other side. The one associated with the midrib is very short and easy to overlook. The other one made it all the way to the intended vein, but missed the first cut terribly; the insect tried to correct this, but missed again.

On a neighboring leaf of the same oak sapling, the insect got it right:

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This one wasn’t so symmetrical, but it also worked out okay:

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In this second example, it is especially obvious that the leaf cutout was left dangling from the major vein in the middle. What did the insect do while the cutout was dangling like this? Five years ago I posted photos of this insect putting the finishing touches on its creation. When I saw these cut oak leaves yesterday, I knew the finished products should be lying on the ground directly below, but none were in evidence. Apparently they rolled a little when they fell; I picked one dead leaf up off the ground and found this under it:

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This little packet was 8 mm long. Congratulations to Laura Hughes for being the only person to recognize the work of a distracted leaf-rolling weevil.

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Curious Leaf Cuts

A week ago today, I stopped by the Montague Plains Wildlife Management Area on my way home from a meeting. Gray birch and various oaks are abundant there, so I thought I’d look around for leaf mines of eriocraniid moths on the newly opened leaves. It turned out to be a little early for them, but I spotted what appeared to be the very beginnings of the mines of a new species of agromyzid fly Julia and I discovered on honeysuckle in Alabama a few years ago. Today we returned to the same honeysuckle plant and found that some of the mines were already completed,  and they were in fact identical to the Alabama mines. So I collected them (fortunately this species pupates within the leaf), and with any luck I’ll have some Massachusetts specimens to include in the type series when I describe the species with Owen Lonsdale. In the intervening week, the birch-mining eriocraniids had come and gone. Oh well. You’ve got to be quick with some of these leafminers.

Anyway, during our walk I noticed these peculiar curving cuts in a leaf, and I was curious whether anyone can figure out what made them. Unlike most mysteries I post here, I already know the answer, which I’ll reveal in due time…
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Bug Rearing 101

[Note: I have made a duplicate of this page here that I will update as needed, and I’m going to leave this one as is, so you might as well just ignore this post and go to the newer version.]

Well, I’ve heard from some people who have found Cecidomyiaceltis deserta galls this spring in Oklahoma, Iowa, and Maryland, but no one has mentioned actually having secured a larva until now. Pete Woods collected several of the galls in Pennsylvania this past weekend and discovered this morning that the first larva had emerged. So, as promised, I’m dropping everything to throw together a page explaining my rearing methods. (Incidentally, if anyone finds these or other mystery larvae I’ve mentioned and doesn’t want to deal with rearing them, I would be happy to take over from there. But people often ask me how I do it, so for a while now I’ve been meaning to make a page like this where I can direct people for answers.)

I collect leaf mines, galls, etc. in standard insect vials (plastic, 9- or 15-dram). If you go looking for these on BioQuip, they’re referred to as “plastic tubes“. You can also get them from Thornton Plastics; if anyone has suggestions of other places to buy them, I’d be happy to add them here. I use a Sharpie pen to write the date, location, and host plant on the lid; this is easily washed off later with alcohol or soap and water when I want to reuse the vial for something else.

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These vials do a good job of retaining the humidity from the leaves, and often nothing more than this needs to be done for a leafminer to complete its development. There is plenty of air in there for an insect to breathe, so no need to punch holes or anything like that. If the leaves (or other host material) are too large to fit in a vial, I put them in a jar or a Ziploc type bag, but if possible it’s best not to complete rearings in bags because adult insects are likely to injure themselves when they emerge (for instance, moths rub off their wing scales, or other insects may deform their wings by cramming themselves into a tight corner).

Some leafminers pupate in the leaves, and in this case you can just wait until the adult emerges. If the leaf starts to dry out (or to prevent a leaf from drying out), I crumple up a square of toilet paper, stuff it in the bottom of the vial, and add a squirt or two of water from an eyedropper. A plastic bag can similarly be humidified with a lightly dampened, folded-up paper towel. For agromyzid flies and certain other things that exit the plant material before pupating, I move the pupae or puparia to a fresh vial with a fresh piece of moistened, crumpled toilet paper. I move puparia from one container to another using a fine-pointed paintbrush; before picking up each one I dip the paintbrush in water. If the larva has spun a cocoon on the vial itself, I leave it in place, removing the plant material to prevent mold and then adding the tissue paper if there wasn’t some already.

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A vial is optimally humid when you can see the slightest amount of fogging on the sides. The vial in the above photo is excessively humid. I use a paper towel to wipe excess moisture from the sides of vials; otherwise there is a risk of the newly emerged adult getting stuck in a water droplet and either drowning or not having its wings expand properly. In the photo below, we’re looking down into the same vial, which contains six puparia of the buckeye-mining agromyzid.

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I check vials once a day to see if anything has emerged or if any humidity or mold control is needed. Many leafminers will emerge as adults within a month or so. These buckeye flies do not emerge until the following spring, and the same is true of the hackberry gall fly (Cecidomyiaceltis deserta) and a number of other insects whose larvae are only active in spring. Species with this kind of life cycle obviously take a little more dedication to rear, and it’s important to check the vials regularly and add drops of water if the tissue starts to dry out. If the tissue starts to get moldy, I transfer the puparia to a fresh vial with a fresh piece of tissue. Erik van Nieukerken uses moss instead of tissue for rearing nepticulids, heliozelids, and other moths. This reduces the mold problem (I’m told), but has the disadvantage of potentially introducing predators, pathogens, or other contaminants to the vial.

Any insects that need to overwinter will need to be exposed to cold temperatures. Their containers could be put in an unheated shed or garage, out of direct sunlight, but then you need to check during warm spells to see if anything is emerging. I like to put everything away for the winter and forget about it, so I use a refrigerator. As far as I know, no insects need to be exposed to freezing temperatures to complete their development, but they need to be exposed to temperatures just above freezing for a certain amount of time. I generally put everything in around November 1 and take everything out around March 1. For a small number of vials or jars, just putting them somewhere in the back of the food fridge would do, but I have a little bug-dedicated fridge in my basement for this purpose. Here’s what it looked like just before I took everything out this spring:

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The fridge is mostly filled with vials in gallon Ziploc bags. In the lower half of the door, you can see a few bags containing larger leaves. On the bottom shelf of the fridge are baby food jars and peanut butter jars containing soil. This brings me to my rearing method for insects other than agromyzid flies that exit their mines or galls to pupate (or are free-living to begin with). Some insects spin a cocoon aboveground, and these I handle in the same way as agromyzid flies. Others (e.g. eriocraniid moths, gall midges, anthomyiid flies, most sawflies, and many weevils and chrysomelid beetles) burrow into soil to pupate. For these, I put a moistened 50/50 mixture of peat and sand in a jar, 3-4 cm deep. The peat helps keep the soil fluffy and its acidity prevents mold from growing. I normally wait until the larvae are mature and wandering around in their original rearing vials before transferring them to a jar of soil, but if I won’t be able to check regularly because of traveling, etc., I put the leaves or galls on top of the soil in the jar, then remove them when I see that the larvae have exited.

The photo below shows a peanut butter jar containing a noctuid caterpillar feeding on a sprig of wintergreen that I’ve “planted” in the peat/sand mixture. These caterpillars take a few months to become full-grown, and I add fresh sprigs of wintergreen as needed. They burrow into the soil when they’re finished feeding and emerge as adult moths about two months later.

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As I already illustrated in my grasshopper post, I take the lids off of the soil jars and put them in Ziploc bags so I can see when adults have emerged. This method, incidentally, is based on the method Ray Gagné has developed for rearing gall midges. I think he has now switched to using 100% peat.

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For groups such as eriocraniids that I know won’t emerge as adults until the following spring, I keep the lids on the jars until I remove them from winter refrigeration. Lidded jars usually retain their moisture well, but those in plastic bags may need a few squirts of water from an eyedropper every once in a while. Because I’m worried about moths rubbing off their scales in plastic bags, when I have a baby food jar with soil containing eriocraniid larvae, I take the lid off of it and put it in an upside-down peanut butter jar. For the wintergreen moths, I just leave the lid on the peanut butter jar, but have to check under the lid every day because this is likely to be where the moth comes to rest when it emerges.

If I’m not sure what an insect’s pupation habits are, I put it in a jar of soil with a piece of crumpled-up tissue paper on top of the soil. Almost all insects will either burrow into the soil or make a cocoon in the tissue or on the soil surface. Some sawfly larvae need a chunk of punky wood to burrow into; Dave Smith recommends providing pieces of cork for this purpose. There is an introduced leafminer on honeysuckle, Perittia herrichiella (Elachistidae), that I had a hard time rearing until I learned that it makes a cocoon on the bark of its host plant, camouflaged with bits of bark. So last fall I put some strips of honeysuckle bark in a vial and added the larvae as they emerged from their mines. The cocoons were so well camouflaged that the larvae just seemed to disappear after I put them in the new vial, but sure enough this spring they’ve all emerged as adults.

I think this pretty well covers it, but I’ll be happy to add further details if anything needs clarification. If anyone has had success with other rearing methods, I’d be interested to hear about them. I’ve done very little with wood-boring and stem-boring insects, for instance, and obviously some different strategies would be needed for these.

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Things To Look For This Spring, Part 3

First, a quick update on the hackberry galls: Mike Palmer has found a bunch of them in Oklahoma, and in fact they may already all have been abandoned there. Some of them have holes near the base, and others have the beginnings of holes in the same place, clearly made from the outside, as if something was trying to get in but gave up. We’re hanging onto them just in case there are some agromyzid larvae left inside, but in any case, I now have a picture of one to reinforce the search image for those of you who are keeping an eye out for them:

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The withering leaves beyond the galls may be the easiest way to spot them. For anyone who finds some to collect, I would recommend cutting the twigs several inches below the gall and putting them in a resealable plastic bag right away to retain moisture. The larvae seem to develop pretty quickly, so I would say go ahead and collect any you find, rather than waiting to make sure they are mature.

Here is the underside of the same gall, showing the presumed larval exit hole:

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Anyway, the third and final(?) thing I’d like you to keep an eye out for this spring is something that has been bugging me ever since I got going on this leafminer business five years ago. During my first visit to Nantucket in September 2011, I got a ride over to the little island of Tuckernuck to spend a few hours looking for insect signs there. One of the leaf mines I found there was this contorted, narrow, linear one on arrowwood (Viburnum dentatum):

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Over the following winter, as I began reviewing all the published information on North American leafminers, it became clear that this wasn’t a mine that anybody knew about. So when I returned to Nantucket in early August of 2012, I made a point of looking for more examples, and I found them to be abundant there. I noticed that they always ended up at the midrib near the base of the leaf, and on close inspection I could see that the mines continued down the petiole.

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As you can see in the above photo, the mine continues for a short distance in the petiole and then goes deeper in the plant tissue, where it can’t be followed anymore. Some mines were visible for longer than others, and after examining several it was clear that this species follows the petiole down into the twig, where it continues to mine deep in the bark. So I cut several sprigs of arrowwood as described above for the hackberry galls—several inches below the mined leaf, with the hope that the mining larvae were still inside. Over the next few weeks, I found three different types of larvae in the bag. There were these yellowish ones, about 1.35 mm long…

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…these whitish ones, which were even smaller…

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…and a single one like this, about 1.5 mm long:

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Eventually I realized that the yellowish ones were larvae of Sackenomyia commota (Cecidomyiidae), the midge responsible for these blisterlike galls on arrowwood leaves:

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The whitish ones may have been larvae of another, inquiline midge species, or possibly of a parasitoid wasp. The third larva, however, bore a striking resemblance to a Marmara larva I’d seen illustrated in a paper. Marmara is a genus of mostly bark-mining moths in the family Gracillariidae, subfamily Gracillariinae. Since I knew Dave Wagner and Don Davis are working on this group, I asked them for their opinion. They both agreed that it looked like Marmara, but neither of them was aware of a Marmara on Viburnum—the only gracillariid recorded from that host is Phyllonorycter viburnella, which is said to be rare even where arrowwood is common, but like many normally rare things, it is common on Nantucket:

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About the Marmara, Dave commented: “If the Viburnum feeder proves to be localized to Nantucket and Tuckernuck Island—a biogeographically bizarre distribution—it would not totally surprise me.  Out West there are many Marmara that exhibit such localized distributions.”

The Marmara larva I had photographed was nowhere near mature, and having seen Marmara bark mines on other hosts like ash and pine, I knew they can be very long—it was no wonder the sprigs I had collected hadn’t been big enough for the larvae to complete their development. Marmara species typically have a year-long life cycle that involves overwintering in the bark, then continuing to feed in the spring and transforming to an adult around June.

In June of 2013, I returned to Nantucket and found that there were in fact bark mines visible on some arrowwood plants, though mostly for short stretches; it was clear that most of the feeding trail was too deep to see, and following it to its end would be impossible.

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Some Marmara species conveniently spin their cocoons at the ends of their mines, but others exit the mine and wander off before pupating, and there was no way to know what this one did. I searched the plants that had visible bark mines, but I didn’t see any signs of cocoons, so I assumed this was a species that wanders off.

The following month, I was doing fieldwork in southeastern Massachusetts (the same job that brought us Orchestomerus eisemani and the scuttle flies I wrote about a few weeks ago) and I spotted some more of the leaf mines—the first examples I’d found off the islands. I collected some more sprigs, knowing I wouldn’t be able to raise larvae to adults, but hoping that once again one would pop out of the bottom of a twig, and this time I’d preserve it for DNA barcoding, to see if it could be matched with some adult Marmara specimen. None ever materialized, but two of these did:

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Recognizing from the horn at the back end that they were some kind of sphinx moth (Sphingidae) caterpillar, and knowing that the host was Viburnum, it was easy to identify them (using Dave Wagner’s guide to eastern caterpillars) as immature hummingbird moths (Hemaris thysbe). I’d had no idea what hummingbird moth caterpillars looked like before then.

On one or two of the Nantucket arrowwood plants, I had seen the Marmara mines going within a few inches of the ground before disappearing again. I mentioned this to Dave, and he thought it was likely that this species overwinters in the bark of the roots. This is not unheard of; the mine of M. basidendroca on green ash (Fraxinus pennsylvanica) extends up to 7 cm below ground before resurfacing for pupation and emergence of the adult.

It looked like drastic measures would be required to learn the identity of this moth. So in the summer of 2014, Julia and I returned to Nantucket and tied pink flagging on several arrowwood plants that had leaf mines. Unfortunately, the mines weren’t nearly as common that year as they had been in 2012. Julia returned in December and dug up and potted the flagged plants. Meanwhile, I had found a few examples of the mines in the Berkshires of western Massachusetts—on wild raisin (Viburnum nudum) and hobblebush (V. lantanoides) as well as on arrowwood—and I had potted a couple of those too. Julia sewed some bags from transparent fabric to surround the potted plants and trap any emerging insects. We kept the plants in our shed all winter.

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Last spring, we brought all the bagged plants into our kitchen and checked them several times a day for any signs of life.

On April 2, this 6-mm sawfly emerged—a male, given its fancy antennae. Dave Smith identified it as a species of Monoctenus (Diprionidae), which would have fed as a larva on juniper foliage, then burrowed into the soil among the arrowwood roots to overwinter and pupate.

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On April 13, this 2-mm wasp emerged. I thought it might be a parasitoid of the Marmara, but it turned out to be an Encyrtus (Encyrtidae), which must have emerged from a scale insect on the bark of the arrowwood.

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Toward the end of April, a moth finally emerged—but it was a tortricid, not a Marmara.

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Specifically, this 8-mm moth was Zomaria interruptolineana, whose larva is a leaftier on blueberry and huckleberry, both of which are abundant on Nantucket. Coincidentally, I’d photographed this same moth species on an arrowwood leaf on June 10, 2013, at the same location where Julia dug up that plant.

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But alas, no Marmara adults ever emerged.

Last July, on our way to Colorado we stopped at a rest area along I-70 in Illinois. The border of the picnic area was lined with forest, so we walked along it to see what leaf mines we could find. There were a couple of arrowwood plants, and we found a few of the Marmara mines. Then, much to my surprise, we found two Marmara cocoons! The species that pupate at the end of their mines make their cocoons under a little bark flap, like so:

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Since this species is sneaky and its mines mostly aren’t visible on the bark surface, it was just dumb luck that we noticed these. Where the bark has been removed in the above photo, you can see a few dark lines, which are the frass trail from the larva’s mine. To give a sense of the scale, as well as a view of the white silken cocoon beneath the bark flap, here’s a shot with my finger holding the bark flap back:

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Of course, both cocoons were already empty, so we had no hope of getting adults from them, but now we know there’s no need to dig up the plants to rear them; we just need to search more carefully for these bark flaps in the spring.  These were several feet off the ground, so apparently the larva doesn’t always mine all the way to the roots—or if so, it may mine all the way back to the height of its original leaf mine.

A closer look at the cocoon under the bark flap reveals that it is decorated at either end with “frothy bubbles.”

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These “bubbles” are expelled through the walls of the cocoon, for unknown reasons, by the larvae of certain genera of Gracillariinae. Interestingly, the Marmara species that spin their cocoons under bark flaps at the end of their mines aren’t supposed to make these bubbles, so it seems pretty clear that this is a new species rather than a described one using a previously undocumented host plant.

Here is a photo of the cocoon of another gracillariid that shows the “bubbles” more clearly:

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When backlit, you can see that they are faceted like little jewels:

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Anyway, if you have any kind of viburnum near you, please keep an eye out for these bark flaps this spring. Of course, it would be easier to know which plants to look at if you had flagged plants that had leaf mines on them last year, but maybe you’ll luck out as we did in Illinois. For whatever reason, I’ve never found the mines in the central part of Massachusetts where I live, even though I’ve found many examples in the extreme western and eastern parts of the state.

And if you don’t have viburnum near you, I’m sure there are many more Marmara species left to discover. In fact, I’m pretty sure the number left to discover is larger than the number that already have names, based on bark mines I’ve found on host plants from which Marmara adults have never been reared. When the mines are fresh (and when it’s not a sneaky species that mines too deep in the bark to see), the larva can be seen through the bark epidermis, as in this example on Ceanothus sanguineus from Oregon (also not a known host for any barkminer):

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Not all bark mines are caused by Marmara species; they can also be the work of other moths such as Zimmermannia, a subgenus of Ectoedemia (Nepticulidae). Or possibly something else. I’m including bark mines in the keys in my leafminer book, because let’s face it, no one is ever going to write a whole book about bark mines.

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