sigmoid prominent

(Clostera albosigma)

Hodges #


sigmoid prominent
Conservation Status

IUCN Red List

not yet assessed


N5 - Secure


not listed




Mid-May to mid-August. Probably two generations per year.


Deciduous woodlands and forests, and shrubby wetlands and fields


Total Length: to ¾

Wingspan: 1 to 1½

          Photo by Bill Reynolds

This is a medium-sized, heavy-bodied, nocturnal moth. It is the most common of the four Clostera species found in Minnesota. The species name albosigma means “white S” and refers to the prominent curved marking on the forewing. Spring individuals are darker with more highly contrasting markings. Summer individuals are paler and less conspicuously marked.

The top of the head, the collar, and the top of the thorax are dark brown. The rest of the body is lighter grayish-brown. The male has a dark brown tuft at the tip of the abdomen.

The forewing is grayish-brown. The forewing is slightly concave on the costal (leading) margin and is rounded at the tip. It is crossed by four pale lines, the basal, antemedial, median, and postmedial lines. The antemedial and median lines are parallel and nearly straight. The median line is broken and does not reach the costal margin. The postmedial line is angled backward, forming a “V” with the median line at the inner margin, and forming a prominent white “S”-shaped bar approaching the costal margin. The white bar sharply delineates a dark reddish-brown or chestnut brown area. The cubitus (Cu) vein appears 3-branched.

The hindwing is nearly evenly grayish-brown without contrasting markings. The subcostal (Sc) vein and the anterior branch of the radius (R1) are fused together. The Sc+R1 and radial sector (Rs) are close together and parallel to at least the basal half of the anterior side of the discal cell then diverge.

The male antennae are comb-like with teeth-like structures on both sides. The female antennae are thread-like.

The caterpillar is stout and up to 13 16 long. It has a dark, proportionally large head, and there is usually a pale brown spot above the face (frons). The thorax and abdomen are yellowish-buff and covered with downy, pale hairs (seta). Between the first thoracic segment (T1) and the second abdominal segment (A2) there are four indistinct orange or yellow lines separated by even more indistinct charcoal lines. There is a black knob on A1 that is nearly twice as large as a similar knob on A8. There is a broad, dark gray subdorsal stripe and a broad orange spiracular stripe. Mature caterpillars are seen from May to November.



Larval Food

Mostly quaking aspen, but also poplar and willow, and sometimes alder, birch, maple, and elm.

Adult Food

Adults do not feed.

Life Cycle

Given the long flying time for this species, there are probably two generations per year in Minnesota.

The pupa overwinters.


Adults are active at night and will come to light. They rest with the wings folded tightly around the abdomen, which is raised into the air.

The caterpillar 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. At night, it feeds in the open. Unlike all other prominents (Family Notodontidae), this species does not squirt acid as a defense.

Distribution Distribution Map  

Sources: 21, 24, 27, 29, 30, 71, 75.





Lepidoptera (butterflies and moths)











No Rank:



No Rank:




Noctuoidea (noctuid moths)



Notodontidae (prominents)





Ichthyura albosigma


sigmoid prominent









Costal margin

The leading edge of the forewing of insects.



The upper part of an insect’s face, roughly corresponding to the forehead.



A usually rigid bristle- or hair-like outgrowth on butterflies and moths used to sense touch. Plural: setae.



A small opening on the surface of an insect through which the insect breathes.






Visitor Photos
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Bill Reynolds

This first image it was trying to mimic a leaf and the second after I disturbed the moth from this side of the barn.

  sigmoid prominent   sigmoid prominent Photos



  Sigmoid Prominent - Hodges#7895 (Clostera albosigma)
Andree Reno Sanborn
  Sigmoid Prominent - Hodges#7895 (Clostera albosigma)  



Visitor Videos
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Other Videos
  Sigmoid Prominent Moth (Notodontidae: Clostera albosigma) Dorsal View
Carl Barrentine

Uploaded on Aug 6, 2011

Photographed at Red Wing, Minnesota (04 August 2011). Go here to see the lateral profile of this specimen:




Visitor Sightings
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Bill Reynolds

Location: Pennington Co. Minnesota

This first image it was trying to mimic a leaf and the second after I disturbed the moth from this side of the barn.

sigmoid prominent






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