I found some more leaf mines

**A leaf mine in a big-leaf aster leaf that was probably made by the larva of an *Ophiomyia* sp., a genus of leaf-mining flies.**

Recently, I’ve become more interested in leaf mining insects after finding what might be the serpentine leaf mine of a Stigmella moth in a blackberry leaf. This wasn’t the first moth leaf mine I have found. In 2017, I identified another leaf mining moth, Phyllocnistis populiella, recognizing it from its leaf mine in a balsam poplar leaf.

Later, in 2019, I found the adult of another poplar leaf mining species, Phyllonorycter nipigon. Beyond that, my findings of leaf miners have been sporadic and by chance when photographing micro-moths at my moth lights.

Changing weather, changing focus

With the colder fall weather, it is more difficult to find insects and other arthropods. So, now I am turning my attention to the signs of them.

Out on my walks in the woods late last month, I came across five more serpentine leaf mines. The first was in a big-leaf aster (Eurybia macrophylla), which is shown in the photo at the top of the page. The other four were in wild red columbine (Aquilegia canadensis), coltsfoot (Petasites palmatus), goldenrod (Solidago gigantea), and bunchberry (Cornus canadensis). I couldn’t find larvae in any of them, but I think I have a good idea of what made them.

**This leaf mine in a columbine leaf was probably made by a larva of *Phytomyza aquilegivora*.**

Possible identifications

The leaf mine in the aster leaf was probably made by the larva of a species of fly in the genus Ophiomyia, leaf mining flies in the family Agromyzidae.

**Phytomyza *agromyzina* in bunchberry**

While I’m not absolutely certain, the leaf mines in the other four plants were probably made by the larvae of leaf mining flies in the genus Phytomyza, also in the family Agromyzidae.

Columbine: Phytomyza aquilegivora
Bunchberry: Phytomyza agromyzina
Coltsfoot: Phytomyza albiceps group (see page 5)
Goldenrod: Phytomyza solidaginophaga

I’ve probably seen the adult Phytomyza flies, but didn’t give them a second thought, assuming they were just some more pesky flies buzzing around my head looking for blood or sweat. Next year, I’ll be paying more attention.

Leaf mining flies are species-rich

There are at least 600 named species of Phytomyza, making it the largest genus of leaf mining flies in the world. Ophiomyia has over 200 species. Species of Phytomyza and Ophiomyia are host-specific, which accounts for much of the diversity in their genera.

Cerodontha is another species-rich leaf mining fly genus in the Agromyzidae, with 285 species worldwide. Cerodontha is a monocot specialist mining the leaves of sedges (Cyperaceae), soft rushes (Juncaceae), irises (Iridaceae), and grasses (Poaceae). Some Cerodontha species have been found in Minnesota and neighboring Wisconsin.

A quick search of species of Phytomyza and Ophiomyia that might occur in northern Minnesota shows at least twenty species and five species, respectively. The number of Cerodontha species in Minnesota is unknown. I think next summer is going to be an interesting one.

Wordless Wednesday

Moths and Their Nighttime Floral Visits

*Xestia normanianus*, a dart moth, nectaring on lance-leaved aster (*Symphyotrichum lanceolatum*) at night.

What do moths do at night anyway? Some of them visit flowers for nectar.

Back in August, I was wandering about in the woods at night looking for foxfire fungi. At the head of the trail on my way out, I saw a sunflower plant with something on the flowers. It was a green tree cricket (Oecanthus) eating the stamens in the sunflower florets.

The next night, I went back but this time with my camera, hoping to find more tree crickets. I had my LED headlamp on like the previous night and used it to illuminate the flowers and foliage where I wanted to photograph. I also set the flash of my camera to “on”.

Although I could hear tree crickets in the bushes, I didn’t see any this time. What I did see were lots of moths on sunflowers and asters. Aiming the lamp’s beam at the flowers, I then pointed my camera at the moths and began taking photos. I wasn’t using a tripod, so many were blurry. Some were also overexposed by the bright LED light. But a few turned out.

*Feltia jaculifera* nectaring on a sawtooth sunflower (*Helianthus grosseratus*)

The moth species (Xestia normanianus, Feltia jaculifera, and Nephelodes minians) I found on flowers at night came as no surprise. These and other dart moth species are common visitors to my moth lights. But it was exciting to see them going about their normal activities in a natural setting. I never did find any foxfire this year.

**Moths weren’t the only visitors to flowers at night. I wonder if this crab spider was sleeping or waiting for a moth.**

Sarea difformis: A fungus that lives on conifer resin

**Black spruce resin with *Sarea difformis*.**

Conifer resin oozing from a tree is an inhospitable place. The terpenoid chemicals in resin are toxic to many forms of life, but not all. Even though conifer resins are full of anti-fungal and anti-bacterial compounds, some organisms have found a way around that. One of these is a fungus called Sarea, a genus of fungi that grows on the resins of pines, spruces, firs, and cedars. Organisms that live on resins are called resinicolous (resin plus “colous” meaning “inhabitant”).

From lichen to fungus

At one time, Sarea was thought to be a lichen, but because it lacks a photobiont (symbiotic photosynthetic organism), it has been “demoted” to a fungus. The tiny (barely 1 mm across) fungus bodies pictured above and below growing on the resin of a black spruce are, to the best of my knowledge, the apothecia (reproductive structures) of Sarea difformis. Cross-sections of the fruiting body examined under a microscope would make identification more certain, but that’s a bit out of my reach right now.

**A few small fruiting disks (marked by red arrows) of the fungus *Sarea difformis* are growing on the darker portions (are those part of the fungal body?) of the resin. Can you find more?**

I have looked for research papers on how Sarea can live on conifer resin, but the results have not yielded much information. Does it actually break down the resin components into simple carbohydrates? If so, then does it do this on its own, or is there a symbiotic relationship with bacteria or another fungus? Are the fungal hyphae growing in the resin or merely on top? How does it disperse? A lot of questions, and I’m sure there are answers somewhere.

Taxonomy

Sarea is a genus in the phylum Ascomycota (cup fungi, sac fungi), which includes familiar mushrooms like morels and the blue mold in Roquefort cheese. The taxonomy of the genus Sarea is not entirely settled, so some species may be moved to other genera, and species from other genera may be moved to Sarea. Also, new species are being discovered.

A similar resinicolous species that might be encountered in northern coniferous forests is Sarea (Zythia) resinae. It can be distinguished morphologically by the color of its apothecia. Sarea difformis has black apothecia, and Sarea resinae has orange apothecia.

Rare?

Sarea is not a rare fungus, but because of its small size and peculiar habitat, it is just rarely seen. It occurs throughout the cooler regions of the northern hemisphere.