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Nature Profile
by Bob Thomas

“Hey, look at this! It looks like a road map on a leaf!” This visitor to a typical Louisiana forest or field has just seen his first leaf miner, an insect larva which lives inside a leaf and feeds on the tissues between the upper and lower epidermis. As it moves about, a trail is produced that gives away its presence. Perfectly adapted for this lifestyle, the larvae are flattened and have reduced or no legs.

There are quite a few different kinds of insects whose larvae are leaf miners, including moths, wasps, flies, and beetles. Each is characteristic for a certain type of plant and creates a predictably-shaped tunnel. Serpentine mines follow a circuitous route and widen as the larvae grow. Blotch mines are irregular “rooms” that may be interconnected by tunnels.

Natural controls for these insects include mites, predacious wasps, and predacious flower bugs.

If heavy infestations occur, defoliation may lead to death of the plant. One of the most commonly infested plants locally is the Mist Flower (Eupatorium) and its relatives. Naturalists report that there is no indication that native herbs are suffering as a result of serving as leaf miner nurseries.