Five years ago this month, Julia and I were nearing the end of our first (and longest) trip around the US in search of leafminers. Walking up a desert wash near Tucson, Arizona, we encountered a leguminous shrub that was later determined to be “rosary babybonnets,” Coursetia glandulosa (Fabaceae).
A number of the leaflets had small, “underside tentiform” mines…
…which we collected in vials. Within a couple of weeks, about 20 adult moths had emerged.
If this all sounds or looks familiar, it’s because I wrote about it nearly four years ago when I was trying to determine what the host plant was. As I mentioned then, I had initially thought this moth would be a species of Macrosaccus because that’s the genus that typically forms underside tentiform mines on legumes, but after I looked at the known species in that genus, I wasn’t so sure.
For instance, here is an adult of Macrosaccus morrisella, which I reared from hog-peanut (Amphicarpaea bracteata):
Here’s Macrosaccus robiniella, from black locust (Robinia pseudoacacia; one wing is a little messed up, but you get the idea):
And here’s Macrosaccus uhlerella, from false indigo bush (Amorpha fruticosa):
All are basically solid orange with bold white markings and varying amounts of black—including a distinct black apical dot—whereas the Arizona moths were white peppered with black, with a little orange here and there. In April 2014, Julia and I visited Dave Wagner at his office in Connecticut, and after taking a quick look at one of the specimens he said it looked like a new genus. He boxed them up right then and there and sent them off to Don Davis, along with a few other interesting moths we had brought.
This spring, I sent Don some unrelated specimens, which after two months had somehow not made it to his office at the Smithsonian. When I asked one day if they had arrived yet, he searched around and found the specimens Dave had sent over three years earlier. Having just described my first moth with Don, I suggested that we do this one too. The genus wasn’t immediately clear to him, even after dissecting one, but ultimately the genitalia and wing venation indicated that Macrosaccus was a good fit after all. So we named it M. coursetiae, and the paper describing it was just published today*.
Here’s another adult of Macrosaccus coursetiae, which happens to be resting on an aborted leaf mine (tentiform mines start out flat and only visible on one leaf surface):
* Eiseman, Charles S. and Donald R. Davis. 2017. A new species of Macrosaccus (Lepidoptera: Gracillariidae: Lithocolletinae) from Arizona, USA. Zootaxa 4358 (2): 385–392.