An auspicious beginning for the fall leafminer season!
Leafminer #191: Ectoedemia populella (Nepticulidae), on quaking aspen (Salicaceae: Populus tremuloides). On the morning of September 22, I went to get the paper and noticed this leaf that had blown onto our driveway from a tree across the road:
The swelling in the petiole at the base of the leaf is an incompletely developed gall of E. populella, which naturally is known as the “poplar petiole gall moth.” Although this species spends most of its larval life feeding in the gall, it hasn’t forgotten its leafminer roots. A close look at the underside of the leaf reveals that the egg was laid on the leaf blade, and the newly hatched larva mined along the midrib and into the petiole before causing the gall to form.
I already had Coptodisca splendoriferella (Heliozelidae) as leafminer #135 back in July, when I found it on black cherry, but I couldn’t resist getting a shot of this nice group of mines on an apple leaf—some of the larvae are still feeding, while others have already cut out their oval cases and dropped to the ground in search of a place to pupate and overwinter.
Leafminer #192: Neochirosia nuda (Scathophagidae), on Canada mayflower (Asparagaceae: Maianthemum canadense). I noticed some mines of this fly on a walk in the woods, and I remembered there are some Canada mayflower plants growing along the north side of the shed. I checked them and sure enough, two of the leaves had mines. On the leaf shown below, there are eight brown eggs along the midrib, but only one of them has hatched so far.
Leafminer #193: Synchysa tricincta (Scathophagidae), on false Solomon’s seal (Asparagaceae: Maianthemum racemosum). This species lays white eggs on the lower leaf surface instead of brown eggs on the upper surface. I had been watching for its mines all year, and finally found one on September 22 on a false Solomon’s seal plant I hadn’t noticed before. The mine was probably formed months ago.
Leafminer #194: Calycomyza malvae (Agromyzidae), on hollyhock (Malvaceae: Alcea rosea). Three new leafminers for the yard on the first full day of autumn was already pretty good, but it suddenly popped into my head to check the pathetic little hollyhocks we planted in the shade behind one of the compost bins this summer, and sure enough, there were a couple of larvae mining away.
The next day Julia and I went to Nantucket for the 10th annual survey of leafminers, gallmakers, and other little-known herbivorous insects there. It was a very successful visit; I’ll have more on that sooner or later. We got home on the 26th, and when I walked around the yard the next day, there were a few more leaf mines to be found.
Leafminer #195: Phyllonorycter kearfottella (Gracillariidae), on Chinese chestnut (Fagaceae: Castanea mollissima).
Leafminer #196: Stigmella sp. (Nepticulidae), on Chinese chestnut. I’m not sure exactly what species this is (no North American species has been reported from Chinese chestnut), but it isn’t either of the Stigmella species I’ve found on oak in my yard this year.
I found a couple of other mines that need a little more investigation to decide whether they’re something new. For now, here are some other things I found as I wandered around the yard yesterday.
On September 6 I’d found these red-humped caterpillars (Notodontidae: Schizura concinna) on the underside of a leaf on the little aspen sapling in the front yard—I wrote that they were in varying stages of becoming “mummified” by braconid wasp larvae spinning cocoons inside them.
When I checked yesterday, I realized that these weren’t actually the caterpillar “mummies” characteristic of braconid wasps in the genus Aleiodes; the wasps here were campoplegine ichneumonids, which spin their cocoons outside their hosts but in some cases wrapped in the host’s skin.
Most of the wasps had already chewed their way out of the cocoons:
In this side view, you can see the white cocoons peeking out under some of the “pelts.”
Nearby, galls of Dryocosmus deciduus (Cynipidae) were bursting out of the midribs of leaves on a little red oak sapling (Fagaceae: Quercus rubra):
The larger red oak sapling in the “upper nut orchard” had some nice fuzzy midrib clusters made by another gall wasp, Callirhytis lanata.
The Tischeria quercitella mines I first noticed on September 5 are coming along nicely.
A little downhill from that oak, a third wave of sawfly #41, which I first noticed as tiny hatchlings, is continuing the work of defoliating the pussy willow (Salicaceae: Salix discolor).
Yesterday the shrub was abuzz with ichneumon wasps trying to lay eggs on these larvae.
They would fly within a few centimeters of the larvae and then turn around and approach them backwards.
Every encounter that I watched ended with the sawfly larva flicking its tail end and the wasp flying away—except in the case of the wasp in the photo above, which was actually knocked off the leaf by the larva immediately after I took the picture.
Back in the “upper nut orchard,” I noticed these elegant poop tubes on the undersides of a few hazelnut leaves; presumably the work of an Acrobasis species (Pyralidae).