Introducing Fenusa julia

The summer before last, Julia and I took a trip out to Colorado and some Midwestern prairies, partly to visit some friends and partly to fill in some gaps in our leafminer explorations (which had taken us all around the perimeter of the US, but had so far missed the whole area bounded by Ohio and California, South Dakota and Texas). One day we were wandering along a creek near Aspen when Julia spotted some mines on a wild rose, which I later determined to be Rosa woodsii.

They were clearly sawfly larvae, but I was sure there were no known rose-mining sawflies in North America, since there are only 30 or so species to keep track of. So we collected a dozen of them, and by the end of the day they were already starting to exit their mines.

Fortunately, I was prepared with a jar of soil for them to burrow into, and within a few days they had all done so. I refrigerated the jar over the winter as described here, and a month after I took it back out of the fridge, seven adults emerged.

I sent them off to Dave Smith to examine, and they turned out to be most similar to Fenusa ewaldi, a species he had described just a few years earlier, reared from larvae mining rose leaves in Russia. The two species look pretty much the same, but he found differences in the antennae, eyes, wings, and ovipositor. Julia had made me promise not to name any flies after her, but she never said anything about sawflies, so I decided to call the new species Fenusa julia. The paper describing it appeared online today, in the so-called April issue of Proceedings of the Entomological Society of Washington*.

Just like Scolioneura vaccinii, which we discovered on our first big leafminer road trip, Fenusa julia is the first native member of its genus to be found in North America. There are also three introduced European species here: F. dohrnii on alder, F. pumila
on birch, and F. ulmi on elm.

* Smith, David R. and Charles S. Eiseman. 2017. A new species of Fenusa (Hymenoptera: Tenthredinidae) mining leaves of Rosa woodsii Lindl. (Rosaceae) in North America. Proceedings of the Entomological Society of Washington 119(2):233-238.