Leafminers Awaken!

As I mentioned, on February 25 all the overwintering bugs got taken out of the fridge, and last night’s check of all the vials revealed the first two emergences.  They both happen to have come from leaf mines in the aster family (Asteraceae), which is what I’m currently working on in my keys to North American leaf mines.


Although I don’t think I would have recognized it from any of the examples shown here, I know this is Acrocercops astericola (Gracillariidae) because of the leaf mine it made as a larva.  This is how the mines on white wood aster (Eurybia divaricata) looked on September 28 when I collected them:


The mine begins with an indistinct squiggle, which is suddenly expanded into a large blotch that may entirely obliterate the linear portion.  The larva eventually eats out most of the green tissue in the blotch, which becomes puffy from the contracting of silk spun inside the mine.  Smaller leaves can look as if they’ve been blown up like balloons, as with this leaf of calico aster (Symphyotrichum lateriflorum) I found in Maine:


When done feeding, the larva turns bright red and emerges from the mine.


It spins a flat, brown cocoon, decorated with a single “frothy bubble”.  Many species in the subfamily Gracillariinae make bubbles like this; some cocoons have 20 or so of them.


As you can see, this leaf was already pretty moldy at the time the cocoon was made, but evidently the cocoon was tough enough to keep out the mold.  Here’s the pupal skin of the moth that just emerged, protruding from the moldy wreckage:


This pupa is facing us, and if you look closely you can see the sheaths of all the legs and antennae tucked into the middle.

The other insect that had emerged last night was a parasitoid wasp.


It’s a eulophid wasp in the subfamily Entedoninae, and I will need a specialist to get any further than that. The object to the right is the agromyzid fly puparium from which it emerged–at the far end you can see the hole it chewed to get out.

As luck would have it, this is from the same batch of fleabane-mining flies I wrote about here.  As I mentioned, I won’t know for sure what the host fly is until Owen Lonsdale examines the specimens (and I sent the poor guy 100 vials of flies all at once, so it may be a while), but now that I’ve made a key to leaf mines on fleabanes (Erigeron spp.), I’m prepared to suggest that the fly is Phytomyza erigerophila.  That species is widespread in Europe; in North America it has only been documented in Alberta, Tennessee, and North Carolina, but there is no reason to think it wouldn’t also be in Massachusetts.

Looking at that previous post about all the leafminers on a single fleabane plant that popped up in my lawn, I realize that I never wrote about the second to last moth that emerged in the fall before I put everything in the fridge for the winter (this being the last one).  There was a single mystery leaf mine that I guessed was the work of one of the “twirler moths” (Gelechiidae), and I wasn’t sure if the larva was still alive because the leaf had decomposed into a soggy strip of brown mush.  Well, on Halloween the adult moth appeared in the vial:


I was correct about it being a gelechiid; more specifically it was something in the tribe Gnorimoschemini, which includes Gnorimoschema gallaesolidaginis, the moth responsible for the elliptical galls on goldenrod stems–along with dozens and dozens of other species, most of which are known only as adults, and many of which still don’t have names.  Terry Harrison took a look at this photo and said it was “one of the bewildering array of composite-mining spp. of the ‘artemisiella’ type.”  The only gnorimoschemine known to mine fleabane leaves is Scrobipalpula erigeronella, which Annette Braun reared from “an irregular mine” at Glacier National Park in Montana.  I know of two living taxonomists who work on these moths; one never responded to my email about this, and I haven’t gotten around to trying the other one yet.  Surely there is no shortage of unidentified specimens for them to go through, but one would hope that a moth whose immature stages have been documented would be considered worth prioritizing.

About Charley Eiseman

I am a freelance naturalist, endlessly fascinated by the interconnections of all the living and nonliving things around me. I am the lead author of Tracks & Sign of Insects and Other Invertebrates (Stackpole Books, 2010), and continue to collect photographs and information on this subject. These days I am especially drawn to galls, leaf mines, and other plant-insect interactions.
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3 Responses to Leafminers Awaken!

  1. donna gagne says:

    this is the way I like to see bugs and other insects. So I can see what they look like.
    I have see some in other books but it seems they are always in black & white and just
    drawn so when I do see them, I’m never really sure what it is. they all look alike. Thanks
    for the new view of things. It really makes things easier to see & decide what to do with
    or about them.

  2. Can’t wait for this book. Am reading your other at the moment and love it. Thank you.

  3. I too so love your photos Charley. You honor and bring out the dignity and beauty of each creature. Thank you for your work and person.

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