Genus Desmia moth
This week we’ll meet a mysterious moth! Meet the Genus Desmia moth. Our pictured magical little moth is either a grape leafroller moth (Desmia maculalis) or a grape leaffolder moth (Desmia funeralis).
The only way to tell these goth moth cousins apart (aside from DNA) is the markings on their bellies. By the time I researched this, our pretty flitter had flown away so their true form will forever remain a mystery.
D. funeralis have a white belly, While D. maculalis have a black and white striped belly.
If you’re ever lucky enough to find one in person, you can try asking them to “roll over!” but the odds of finding one are slim and finding one who can roll over on command are slim to none. But we can dream.
What we do know about our pictured desmia is that he is a he. Males of both species have that fabulous and distinct notch about halfway along their antennae. Of all the similar looking species, only leafroller and leaffolder males have that nifty fashion accessory.
To be clear, they aren’t impossible to find – I’ve seen a few each year. What is practically impossible, however, is finding one that will sit still long enough to be photographed. Additionally, they are small moths, with a wingspan of just under one inch, so they are easy to overlook.
Due to their flighty nature, there is only one recorded sighting for Oregon on BugGuide and only nine on iNaturalist (two and 10 if I ever got around to contributing my photos).
There are just over 18,000 recorded sightings of desmias in the United States, so flighty nature or not, they still fall under the “uncommon” category in Oregon.
What’s in a name? Whether rolling or folding grape leaves, desmias do indeed have a penchant for grapes.
Don’t panic though; with a mere nine sightings they aren’t going to destroy Oregon’s wine industry.
Both rollers and folders need plants in the Family Vitaceae which includes grapes and Virginia creeper along with 908 other species. So their “grape” common names don’t mean their caterpillars need “grape and only grape” as host plant.
To be fair, in my yard they probably are munching on (and rolling or folding) grape leaves as I have a small wild western grape (Vitis californica) growing in an inaccessible part of the yard. Many yards throughout our area have those wild grape plants; they’re the ones with the small yellow-green grapes.
Do desmias really roll and fold? The caterpillars do! It isn’t known whether leafrollers only roll leaves and leaffolders only fold leaves. In fact, maculalis and funeralis were thought to be one species until fairly recently. The “folder/roller” monikers are a way to further differentiate which species is being discussed.
While they grow the caterpillars of both desmia species munch on leaves. The rolling or folding happens when it’s time for them to pupate (AKA form a cocoon). They’ll build a protective fort by rolling or folding a leaf around themselves and secure it with silk so they have extra protection for that final juvenile life stage.
It’s likely adult desmias feed on nectar, so probably pollinate grapes and creepers, but that’s not a certainty. It could take years before we have more information on the food plant preferences and habits of adults. In addition to being small and shy, they are also nocturnal, and their inky black base color provides brilliant nighttime camouflage making them extra hard to study.
Desmias are the ultimate mysterious goth moth.