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Bug of the Week is written by "The Bug Guy," Michael J. Raupp, Professor of Entomology at the University of Maryland.

Mystery of the frass revealed: Camouflaged looper, Synchlora aerata


Blossoms sprinkled with frass are a clue that a hungry caterpillar is near.


While working in my flower bed last week, I noticed a liberal sprinkling of caterpillar frass on the leaves and blossoms of my chrysanthemums. Frass is a euphemistic term for the pellet-like, powdery or sawdust-like excrement of herbivorous insects. Frass often provides a clue to the presence of an herbivore on or in a plant.

Goldenrods are another favored host of the camouflaged looper. (Do you see the looper in this picture?)

A thorough inspection of my mum failed to disclose the culprit, but as I watched the plant over a leisurely cup of coffee, I noticed a small cluster of flowery debris swaying on a blossom. A closer inspection revealed a cleverly disguised caterpillar cloaked in purple busily dining on the flower. Earlier in the week, I met the cousin of my chrysanthemum caterpillar dining on the petals of a daisy at a nature center.

 The camouflaged looper, Synchlora aerate, can often be spotted performing a herky-jerky waltz partnered with foliage and flower heads as it moves from one meal to the next. This little trickster gathers pieces of vegetation and arranges them on its back in much the same way a warrior might incorporate leaves and branches into a camouflaged uniform to hide from the enemy.

The camouflaged looper turns into a beautiful emerald green moth.

The looper occasionally swayed back and forth as I watched, which added to the illusion of a plant part being blown by the wind. Loopers are members of a large family of moths known as geometrids. The name geometrid derives from Greek roots meaning earth measurer. Another common name for geometrid caterpillars is inchworms, and as loopers and inchworms move along, they do appear to measure the earth inch by inch. In addition to my chrysanthemums, camouflaged loopers eat many types of flowers including ageratum, aster, black-eyed Susan, boneset, daisy, goldenrod, ragweed, raspberry, rose, sage, St. John’s wort, and yarrow. The adult moth of the camouflaged looper is known as the wavy-lined emerald and it is every bit as beautiful as the larva. So next time you see some unexpected frass on your flower blossoms, take a few moments to observe your flowers with an eye out for these masters of disguise.

Bedecked in flower petals, the camouflaged looper makes a fine meal of my chrysanthemums


Bug of the Week thanks Dr. Shrewsbury and the volunteers at the Robinson Nature Center for photographs and the inspiration for this week’s episode. The wonderful reference “Caterpillars of Eastern North America” by David Wagner was used as a reference for this Bug of the Week.