Texas Parks & Wildlife Magazine   




Gallmakers and Leafminers

As leaves unfurl, look for tiny creatures transforming them into art.

Every leaf of every tree and wildflower near your home is a tiny stage for glorious acts of creation and amazing feats of survival. Moths and beetles, flies and mites, wasps and aphids are the artists on the stage.

Find a cedar elm on a warm spring day anywhere in the eastern two-thirds of Texas, and you will probably see some of its rough, toothy leaves sporting stylish reddish bumps covered in fine white fuzz. These structures are called galls.

Galls are exquisite artworks; they can look like balloons, teacups, pinecones, flowers, spires, columns or doughnuts. They can be colorful, hairy or textured. Each one is the result of a creative partnership between a gallmaker and its host plant.

Galls provide everything a gallmaker needs: food in abundance, protection from danger and a nursery for its young. 

Galls on-Leaf-on-Lichen-Covered-Rock

Gallmakers give plants chemical instructions that tell the plant how to make a gall from the building blocks it already has inside. The plant possesses everything it needs to make a gall, but it doesn’t know how to do it until it receives instructions from the gallmaker.

Greenbrier Leaf-with-Leafminer-Trails-8681

As you study leaves and twigs, looking for gallmakers’ handiwork, you’ll find evidence of other dramas, too: odd blotches and spirals, or long, snaking trails across leaves and even prickly pear pads. These are the work of leafminers.

Leafminers are immature insects so small they can live in between the layers of a single leaf. As they eat certain plant cells inside the leaf, they create intricate patterns called mines.

The leaf’s exterior surface protects leafminers from weather and predators as they feast on the bounty inside. Once they’ve eaten enough, they form a pupa and emerge as winged adults into the outside world.

Leafminers and gallmakers are everywhere: urban gardens, country roads and state parks. You can find them while gardening, hiking, hunting and birding. Once you start to spot them, it’s hard to stop. A real-life treasure hunt.

Remember the reddish, fuzzy galls on cedar elm leaves? The mite species that creates those galls is officially unknown to science. In fact, many of the gallmakers and leafminers on common Texas plants have never been formally studied or named.

Maybe you can help give them names. By sharing your discoveries in the gall and leafminer projects on iNaturalist.org (or with your local state park, Texas Master Naturalist chapter, college or university), you can shine a spotlight on these truly wild Texas artists.

 Steven Schwartzman

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