Two years ago I wrote about the striking pink and yellow moths I found resting on evening primrose (Oenothera biennis) flowers by my mailbox, and how I later found the caterpillars feeding on the young seedpods. That same summer, I found two other kinds of moth larvae feeding on the evening primrose plants along my driveway. One was a leafminer I had reared before from the sundrops (O. pilosella) in my mother’s garden, but hadn’t noticed on evening primrose before.
Like nearly all leaf mines on the evening primrose family (Onagraceae), these linear ones on Oenothera are made by a species of Mompha—in this case M. argentimaculella.
Mompha argentimaculella was supposed to be the only leafminer on Oenothera, so I was surprised when one day I noticed distinctly different mines on the evening primrose along my driveway. Instead of narrow, linear mines with frass deposited all along their length, these were blotches with all the frass packed at the beginning.
In one case I found two larvae whose mines had merged.
The reddish larvae were superficially similar to the Mompha larvae…
…but the adults turned out to be something entirely different: Aristotelia isopelta (Gelechiidae).
There was no published host or natural history information available for this species, nor was there any reason to suspect an Aristotelia, since members of this genus are normally leaftiers. However, when I sent a specimen to Jean-François Landry to deposit in the Canadian National Collection, he informed me that they have other specimens reared from evening primrose in Quebec in the 1960s. Also, Terry Harrison told me he once had this moth emerge from a batch of leaves from California that also contained Mompha leaf mines. Terry’s leaves were not evening primrose but Epilobium, another member of the same family. Epilobium species are known as “willow-herbs”, apparently because of their willow-like leaves.
Their seeds are also dispersed on the wind by tufts of fluff in a way somewhat similar to willow seeds. The long, curved, empty seedpods give the dead plants a distinctive look in the winter:
That same summer I was finding all the interesting evening primrose moths along my driveway, I was working in wetlands all over western Massachusetts and kept finding leaf mines on a common wetland plant, Epilobium ciliatum.
These certainly looked Mompha-like, but the only Epilobium miner known to occur in eastern North America was M. epilobiella. This is an introduced European species that starts out as a leafminer, but older larvae feed externally in clumps of webbed leaves. I collected a bunch of larvae, and they continued mining leaves throughout their development. Here you can see one larva spinning a cocoon on the underside of a leaf while two more, nearly mature larvae mine toward it (as you can also see in the above photos, these larvae mine belly-up):
The adults were pretty little orange-marked moths:
Jean-François and Terry concurred that they were Mompha locupletella, a species previously known only from Europe. Unlike M. epilobiella, however, this appears to be a native Holarctic species that simply was missed by earlier microlepidopterists—or at least, no one had gotten around to publish anything about it. There are at least a couple of other Mompha species in this category, another being M. raschkiella, which feeds on fireweed (Chamerion angustifolium), a plant formerly placed in the genus Epilobium. Mompha raschkiella was described from Europe in 1839 and has been found all across Canada, but its existence in North America wasn’t published until 2010. For details of many other Mompha species that have yet to be documented or even named, we’ll have to wait for Terry’s big publication on the genus, which is still some years off. But in the meantime, I summarized what is known about the leafminers of the evening primrose family in a paper that was published recently alongside the one describing Zygoneura calthella:
Eiseman, Charles S. 2016. North American leafminers (Lepidoptera: Gelechiidae, Momphidae) on the evening primrose family (Onagraceae): new host, parasitoid, and distributional records. Proceedings of the Entomological Society of Washington 118(4):510-518.