Flatid planthoppers (family Flatidae, order Hemiptera) are relatively small insects with the adults measuring no more than around 1/4" in length. The adults and immatures (nymphs) look nothing alike which can lead to identification issues with connecting one to the other.
The adults of many species have broadly triangular shaped front wings that they hold tent-like over their abdomens. The adults are commonly found resting on plant stems and are often mistaken for moths.
A good example is provided by the Citrus Flatid Planthopper (Metcalfa pruinosa). Despite its common name, this planthopper is commonly found in Ohio. It ranges throughout the eastern U.S. from Maine to Florida where true to its common name, it's often found on citrus.
Early instar nymphs are often obscured by a dense cloak of tangled waxy, white, cotton-like "fluff." They congregate in groups, or "colonies," and their profusion of flocculent material on plant stems may cause them to be mistaken for woolly aphids or mealybugs. Late instar nymphs look like some form of Star Wars troop vehicle with tufts of white filaments streaming behind.
Clusters planthopper nymphs are appearing on plants in southwest Ohio. They are most commonly found in woodlands, but will occasionally creep up the stems of plants in landscapes as well as vegetable gardens. They are most often found near the ground; however, I was surprised to find fluffy clusters at around eye-level on the stems and leaves of several woody ornamentals.
Like their aphid, mealybug, and soft-scale cousins, flatid planthopper adults and nymphs use their piercing-sucking mouthparts into phloem vessels to tap plant sap. They discharge the excess sugar-rich liquid from their anus in the form of a sticky, sugar fluid called "honeydew" which can become colonized by black sooty molds.
Fortunately, flatid planthoppers seldom rise above the status of nuisance pests. However, their resemblance to other sucking insects that cloak themselves in white, cotton-like material can lead to misidentifications.
Nymphs can be washed from plant stems using a coarse stream of water from a garden hose which will also wash away the white "fluff." Insecticide applications are seldom warranted, but if needed, insecticidal soap applications are highly effective and will preserve the hopper's natural enemies.