Previews of Parasitoids

Lately I’ve taken to getting backlit shots of leaf mines by removing one of the Twin Lite flash heads and holding the leaf on top of it, so that when the flash goes off the mine is illuminated from both sides.  This allows me to get a detailed look at what is going on inside the mines, and recently I’ve spotted a few parasitoid wasp larvae by doing this.

Here is a shot I took of an agromyzid fly mine (Phytomyza sp.) in an aster leaf (Symphyotrichum sp.) collected in Ohio. In ambient light, I couldn’t quite tell whether the fly larva was still inside or not.

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Looking at the end of the mine, I saw that something was amiss.

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At the very end of the mine (to the left in the photo above), you can see the shriveled remains of the fly larva. To the right, there are three little greenish wasp larvae that have wandered a short distance back down the mine. I took those photos on September 28, and from October 10 to 16, three of these little wasps emerged:

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They are about 1.5 mm long and are some type of eulophid, but not one of the kinds I commonly get from leaf mines.

On October 9, I picked up a recently fallen red oak (Quercus rubra) leaf containing a number of tiny Bucculatrix leaf mines.

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Taking a closer look at the mine above, I saw that the moth larva was still inside–and that there was a wasp larva feeding inside it.

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The moth larva’s head is pointed down, in the lower right corner of the photo. Along the upper edge of the wasp larva, you can see several little pseudo-legs, reminiscent of the ichneumon wasp larva in this post. Based on that, I suspect this is the larva of a wasp in the related family Braconidae, which is the main type of parasitoid that emerges from leaf mines other than Eulophidae. In another post, I showed a braconid that emerged from a Bucculatrix larva that had been parasitized after emerging from its leaf mine.

For more fun with parasites, check out the new National Geographic cover story by Carl Zimmer.

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Smooching Salamanders

The other day I was perusing my folders of salamander photos to find some my sister-in-law could use in a slideshow. I came across the ones below, which I took in March 2004. They are maybe the worst photos I will ever post here, but they document an interesting phenomenon I haven’t witnessed since: red-spotted newts kissing underwater.

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There were multiple pairs doing this, and I don’t remember if these photos all show the same couple. Their behavior wasn’t all as gentle as in the above three photos. Some pairs were violently thrashing around.

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Eventually I had to intervene to see what was going on. I scooped a pair out of the pond, and in a moment they separated…

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…to reveal that they had been stuck together because they had been eating opposite ends of the same earthworm! Like the spaghetti scene in “Lady and the Tramp,” but more like the parody of it in the Simpsons episode “Two Dozen and One Greyhounds,” which ends with the dogs snarling and fighting over the spaghetti.

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Monthly Mystery #23: A Frothy Balloon

Although unidentified leaf mines are the main mysteries occupying my mind lately, I don’t want y’all to get burned out on that topic, so I just spent a little time searching through my photo archives for something else to ponder. I came across this 4-mm object I had photographed on July 1, 2008, somewhere near Asheville, North Carolina.

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My impression at the time had been that it looked something like a green lacewing cocoon. But besides being a little too large (green lacewing cocoons seem consistently to be 3 mm long), magnification reveals that this object is composed of some kind of hardened frothy material, rather than silk, as is the case with this green lacewing cocoon I found on a nearby leaf:

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My current suspicion is that the mystery object is a nuptial balloon dropped by a dance fly (Empididae) in the genus Empis, subgenus Enoplempis. These are fascinating flies that I hope to get to see in action someday. Males of some species offer prey items to females and can be seen carrying them in flight, as shown here. Males of other species package their gift in a frothy balloon, as seen here. Others, such as E. snoddyi, go a step further and offer females empty frothy balloons like this one. Apparently the timing of my July 1 discovery is reasonable, since this E. snoddyi was photographed carrying a balloon in North Carolina on June 25. According to BugGuideE. snoddyi is the only balloon fly in the southern Appalachians, so if I’m right in supposing this object was made by a dance fly, it apparently can be attributed to that species. Anyone have any other ideas?

Based on the current BugGuide mapEnoplempis is not found in the northeastern US, so I guess I will have to head south (or west) some spring if I want to see these flies. However, members of a related genus, Hilara, make similar nuptial balloons using silk rather than froth. I have seen a single Hilara individual not far from where I live in western Massachusetts:

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…so maybe there’s hope that I’ll get to see them carrying their silk balloons around here someday. As you can see, Hilara males have big Popeye-like forearms. When I started writing this post, BugGuide had no photos of males with balloons identified as Hilara, but I just noticed that the ones in this swarm have the same swollen fore tarsi.

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Buckeye Petiole Borer

Back in May, I posted a mystery I had encountered a week earlier involving caterpillars boring in petioles of Ohio buckeye (Aesculus glabra). I’ll copy and paste the relevant photos below, but for explanations you can check out the original post.

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That last photo was taken on April 27. On May 11, a larva appeared outside of the petioles, and its bloated, stiff-legged appearance made me wonder whether it was parasitized by some kind of mummy-wasp larva.

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Two days later, it had become darker and more hardened, which seemed like progress toward rearing an adult wasp…

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…but nothing ever came of it. As you can see, things were getting pretty moldy in the rearing vials. So I was surprised and delighted when a healthy-looking moth pupa suddenly appeared on May 24.

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A couple of other pupae appeared, and on June 2 the first of two adult moths emerged.

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As I had mentioned in a comment on my original post, my prime suspect was Proteoteras aesculana (Tortricidae), which has been given the common name of “maple twig borer,” but whose Latin name is clearly a reference to its having originally been found on buckeye (Aesculus). I checked photos of adults, and the wing pattern and coloring seemed similar, but I was concerned that my moths lacked the prominent wing tufts that are present on all of the examples on BugGuide.

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Recently, I sent a few reared moths to tortricid specialist John Brown at the Smithsonian. Yesterday, he reported back with the identifications, and he listed the above moth as a female P. aesculana. However, a little while later he wrote back and said: “I was putting your specimens in the collection when it occurred to me that your Proteoteras aesculana may be Zeiraphera claypoleana. I’ll dissect it and see what the tail says.” This morning, he reported: “The female Proteoteras is indeed Zeiraphera claypoleana.”

Zeiraphera claypoleana, it turns out, has been given the common name “buckeye petiole borer.” According to BugGuide, it was originally described from Ohio, and Ohio buckeye was given as the host plant. So clearly I haven’t discovered anything new here (in contrast to another of the moths John identified, which apparently had never been reared before, and is the solution to another one of my Monthly Mysteries. But I’ll save that for another time).

One curious thing I just noticed, when picking out photos, is that the other moth I reared from the buckeye petioles (which I did not send to John) looks totally different:

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With that dark patch on its back, it looks much more like the one example of this species that is currently on BugGuide. Somehow, without magnification, the two pinned and spread specimens didn’t appear strikingly different, so I didn’t give much thought to which one I should send out for identification. The pinned example on Moth Photographers Group doesn’t seem to have the dark patch, so I guess this is just a very variable species.

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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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