Subject: Elm Leaf-miner
Location: Fort Collins, CO
May 20, 2012 5:03 pm
There’s more than one species of Elm Leaf-miner, and I can’t discern between them, but this is one of them anyway.
Thanks for sending your photos. This is a first for our site and we did a bit of quick research and we believe we have a proper identification for you. The problem with the common name Leafminer is that it is a name that cuts across many taxonomic orders. Like Galls which can be caused by Flies, Moths, Mites and Wasps, the same can be said of Leaf Miners. According to the Colorado State University Extension website: “Leafminers are insects that have a habit of feeding within leaves or needles, producing tunneling injuries. Several kinds of insects have developed this habit, including larvae of moths (Lepidoptera), beetles (Coleoptera), sawflies (Hymenoptera) and flies (Diptera). Most of these insects feed for their entire larval period within the leaf. Some will also pupate within the leaf mine, while others have larvae that cut their way out when full-grown to pupate in the soil.” The site goes on to state: “Sawfly Leafminers. Most sawflies chew on the surface of leaves, but four species found in Colorado develop as leafminers of woody plants. Adults are small, dark-colored, non-stinging wasps that insert eggs into the newly formed leaves. The developing larvae produce large blotch mines in leaves during late spring. The sawfly leafminers produced a single generation each year.. Elm leafminer (Kaliofenusa ulmi) is the most important species, being locally common in several Front Range cities where it develops on American, English and Siberian elms.” A different scientific name is provided for the species on BugGuide, where it is identified by the abbreviated name Fenusa ulmi. The University of Illinois Extension Home, Yard & Garden Pest website identifies a weevil that is also called the Elm Leafminer, but we believe your culprit is the Sawfly. The Elm Flea Weevil is Rhynchaenus alni.