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