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.
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:
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:
The moths sported endearing pom-poms on their foreheads:
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 (Phyllonorycter, Cremastobombycia, and Porphyrosela).
* 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).