Using Bugs to Identify Plants

Thanks to everyone who weighed in on the mystery plant!  I added a note at the end of that post, but the consensus seems to be that the plant is redberry (Rhamnus crocea, or possibly R. ilicifolia).

Here’s another one, this time from the Sonoran Desert of southern Arizona.

DSC_4942 DSC_4943

You can see some of the incomplete linear leaf mines in the above photos, and here is a complete one that nearly covers one of the smaller leaves:


Exactly a month after I collected some of these mines, this 2-mm agromyzid fly emerged:


This is the only adult fly I got, and unfortunately it was a female, which means that Owen Lonsdale was only able to identify it to the genus Calycomyza.  For most agromyzid flies, species-level identification requires examination of male genitalia.

For reasons I don’t now remember, I had guessed that this plant was something in the aster family (Asteraceae).  Mines have been described for a dozen Calycomyza species that feed on members of the aster family, and all of them make blotches rather than linear mines like the one from which this fly emerged.  The only Calycomyza species that comes to mind that produces linear mines is C. malvae, which feeds on various members of the mallow family (Malvaceae).  It certainly seems plausible to me that this plant is some kind of mallow, having seen desert mallows with leaves ranging from this to this.  Any thoughts on what it might be?

I may or may not be on the right track in this case, but noticing what kinds of insects and mites are living on a plant can be a nice quick way to identify the plant.  I often recognize black cherry (Prunus serotina) by the Eriophyes cerasicrumena (Eriophyidae) galls on the leaves, or poison ivy (Toxicodendron spp.) by the distinctive leaf mines of Cameraria guttifinitella (Gracillariidae), before I am close enough to see the distinguishing features of the plants themselves.  I at first thought this vine was some kind of morning glory (Convolvulaceae) until I saw some milkweed aphids (Aphis nerii) on it and realized it must be something in the milkweed family (Apocynaceae), although I still haven’t figured out exactly what it is.

I should note that even if this plant does prove to be a mallow, that doesn’t necessarily mean the fly is C. malvae.  That species is only known from eastern North America, as far as I can tell.  But if not that species, it would seem to be something very closely related.  I think very few people have ever bothered to look for leaf-mining flies in the Sonoran Desert, so it could easily be an undescribed species.  Someone will have to collect some more of these mines and rear some adult males to get to the bottom of this.

Added 11/12/2013: See update at beginning of this post.

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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9 Responses to Using Bugs to Identify Plants

  1. Where was the milkweed related vine picture taken?

    • That was in southwestern Texas. This info used to be prominently displayed, but Flickr keeps changing things around. If I had known they were going to hide all my location data I wouldn’t have bothered to enter it.

  2. John Pearson says:

    Hi Charley, your milkweed is likely a species in the genus Cynanchum.

    • Thanks–are you familiar with the genera Funastrum and Matelea? Those also occur in Texas and include some twining species, but I haven’t looked through all the possible species yet to see if they can be ruled out.

  3. Ms. Carol Gracie says:

    I don’t know SW desert plants, but the leaves look much like those of some species of Sida (Malvaceae) that I have seen in other parts of the world.

    Carol Gracie

  4. Mark Fox says:

    Along the same lines, I have been using Bugguide posts to track the changing distribution of an undescribed* adventitious Gracillariid moth of unknown (presumably Chinese) origin that exclusively feeds on Chinese tallow tree. In at least two instances (SC, TN, and OK), the first photos of the moth for a state appeared on bugguide weeks or months before the presence of the host tree was documented anywhere in the vicinity!

    So I guess my point is that if you can document the dependent member of an obligate consumer-host relationship, you can infer the presence of the host. To me, this case is extra noteworthy because the tree is a super noxious invasive that is being actively tracked by the USDA, meaning that passive surveillance of an unnamed tiny grey moth by moth enthusiasts has scooped the active surveillance of one of “america’s most wanted” invasive plants by a huge organization.

    Also, I agree that the desert leaves look similar to Sida. And I impressed a botany student on a field trip by identifying a Matelea vine by recognizing a swamp milkweed beetle feeding on it.

    *the species description of the moth will appear in an upcoming issue of Proc.Ent.Soc.Wash.

    • Yes, that’s a great example/application of what I’m talking about–and I’m glad to hear that moth is finally getting a name! I’ve already got your 2012 American Entomologist paper in the bibliography for my leafminer book.

  5. Pingback: More Mallow Miners | BugTracks

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