Sigmoid prominent (Clostera albosigma) is a medium-sized, heavy-bodied, nocturnal moth. It is the most common of the four Clostera species found in Minnesota. Adult moths are found from mid-May to mid-August in deciduous woodlands and forests, and in shrubby wetlands and fields.
A sigmoid prominent adult has grayish-brown wings, a dark brown head and upper thorax, and on the male, a dark brown tuft at the end of the abdomen. The wings are crossed by four pale lines. A dark, chestnut-brown area near the end of the forewing is sharply delineated by a prominent white “S”-shaped bar. The species name albosigma means “white S” and refers to this marking. Spring individuals are darker with more highly contrasting markings. Summer individuals are paler and less conspicuously marked.
The caterpillar feeds mostly on quaking aspen, but also on poplar and willow, and sometimes on alder, birch, maple, and elm. It is a solitary feeder. During the day it curls up a leaf of a host plant and sticks it together with silk webbing, make a shelter where it can feed in safety. Adults do not feed.