Moths from a Desert Legume

Okay, it looks like the identity of the cherry-ish plant from the northwestern US in my last post is going to remain a mystery, but maybe this plant from the desert Southwest will fare better?  This leguminous shrub (Fabaceae) was growing in a wash somewhere near Tucson, Arizona, and naturally it had no flowers or pods, so all we have to go on are its twigs and leaves.

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Like the plant in my previous post, this one had “underside tentiform” mines, which are characteristic of certain moths in the family Gracillariidae.  This shrub’s leaflets were small enough (13 mm or so) that the mines entirely consumed them.   There are two in the photo below:

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Because the leaflets were so small, and because I was pretty sure this wasn’t one of the known host plants for any gracillariid, Julia and I filled a couple of vials with a good number of them.  A little over a week later, the adult moths began to emerge from their pupae, which were thrust through the leaf’s lower epidermis at one end of the mine:

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The moths sported endearing pom-poms on their foreheads:

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Three years ago, all of the North American Phyllonorycter species that mine in leaves of woody legumes were moved the the genus Macrosaccus.  The only species known to occur in Arizona is M. neomexicanus, which mines leaves of New Mexico locust (Robinia neomexicana), which I’m pretty sure this plant was not.  Also, I just checked the illustrations in Davis & De Prins (2011)*, and to me this doesn’t look much like any Macrosaccus.  I think it has to be either that or a Phyllonorycter, and this could be settled by examining the genitalia or wing venation, but such things are beyond me.  Before I ask a specialist to take a look at the specimens, I’d like to know what the host plant is.

I have about 20 of these moths, and amazingly just one parasitoid emerged (it wouldn’t be unusual to have that ratio reversed).  I sent that wasp to Christer Hansson last year, and he identified it as Chrysocharis walleyi (Eulophidae).  Interestingly, I reared C. walleyi from three other moth species last year, each belonging to a different genus that produces underside tentiform mines (PhyllonorycterCremastobombycia, and Porphyrosela).

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* Davis, Donald R. and Jurate De Prins. 2011. Systematics and biology of the new genus Macrosaccus with descriptions of two new species (Lepidoptera, Gracillariidae). ZooKeys 98:29-82.

Added 1/29/2014: The plant has been identified as Coursetia glandulosa (rosary babybonnets).  This is not a known host for any leafminer; apparently the only moth in the world recorded as feeding on this plant is the giant silk moth Rothschildia cinctus (Saturniidae).

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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8 Responses to Moths from a Desert Legume

  1. Sue Cloutier says:

    Our friend, Jim Brock, who lives in Tucson and knows plants that butterflies use said “It looks like Senna leptocarpa but w/o flowers or exact location I can’t be sure.” So, if you can give more on the location/habitat, he may be able to confirm.

    • Thanks for showing these photos around! This was growing in the middle of a dry wash on the west side of Tucson, but unfortunately I don’t remember the name of the place. It was a bushy shrub, maybe 5-7 feet tall. The photos I’ve found for that species (e.g. this one) don’t seem like a close match to me. Senna hirsuta var. leptocarpa appears to be the preferred name these days.

  2. Jim's Blog says:

    Charlie, I know almost nothing about moths and such, but I was going to suggest that the plant is a locust species. Note the thorns and the compound leaves. Just my $.02…

    Jim

    • Hi Jim– There are just two locust (Robinia) species in the Tucson area, black locust and New Mexico locust. This is neither of those–the thorns are very different (these were really just pointy stipules, I think), and the leaflets are smaller and narrower. I agree that the leaves are superficially locust-like, but there are lots of things in the Southwest with similar pinnately compound leaves, and I have no idea how to tell them apart.

  3. Sue Cloutier says:

    Thank you, Charley. Jim wrote back that “5 – 7 feet tall is too large for hirsuta (leptocarpa). Need a specimen.” So maybe next time you are out in Tucson, you can get the species in bloom or contact Jim – you would have a good time with him in the field.

  4. Larry Daloz says:

    I’m no southwesterner, but could it be a Mesquite of some kind. Looks like what I saw recently in the Sonoran area.

  5. Michael Wilson says:

    Charley,
    Your plant is Coursetia glandulosa. You can check images on the web.

    M. Wilson

    • Thanks! I just found your comment, which was in my Spam folder for some reason. I’ve arrived at Coursetia glandulosa based on opinions from two botanists in the Southwest, and I’m glad to have that ID re-affirmed. This is the first record of any gracillariid moth in the world mining in Coursetia.

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