Clostera apicalis (Walker, 1855)
Apical Prominent Moth
Clostera apicalis is a common medium-size (FW length 12–16 mm) with slightly mottled medium to dark gray forewings with a pale lines and a white S-shaped mark on the distal costa that flies in forests during the spring and summer. The costal margin of the forewing is weakly concave and the apex is bluntly pointed. The forewing is mottled gray, darkest on the lateral side of the lines and on the apical distal third. Dark brick-red is present in the anterior subterminal area, sometimes extending to the outer margin. The transverse lines are pale yellowish off-white. The basal line is off-set at the cubital vein. The antemedial line is smoothly excurved. A pale line connects the mid-antemedial line to the postmedial line at the posterior margin which gives the appearance of a long oblique line across the entire median wing. The postmedial line is nearly parallel to the outer margin except at the costa where it forms a pure white S-shaped mark. The discal spot is small, pale gray filled with darker gray. The hindwings are light to medium gray, darker toward the outer margin, with a pale gray fringe. The head and anterior thorax are dark brown, contrasting with the gray rest of the body. The antennae are bipectinate and the tip of the male abdomen is tufted.
This is the most widespread and common species of Clostera in the Pacific Northwest, and can be identified as belonging to this genus by the S-shaped white mark formed by the anterior postmedial line. It can be distinguished from the species in the genus by the straight oblique line across the median area. This line is either absent or waved in the other species. Clostera apicalis has more red near the forewing apex than any other Northwest Clostera.
This species is common and widely distributed in both forest and riparian habitats. These include coastal rainforests, mixed hardwood forests west of the Cascades, high elevation montane conifer forests, and riparian habitats in canyons east of the Cascades.
Clostera apicalis is widely distributed in forests and riparian areas throughout the Pacific Northwest, extending north to the Peace River region of British Columbia. It is least common in arid steppe environments, with relatively few records from the Columbia Basin, southeastern Oregon, and southern Idaho.
This is the most widely distributed Clostera in North America. It ranges from coast to coast, as far north as Montreal in the East, and at least as far south as the Mexico border.
Larva is a foodplant specialist on the Salicaceae, including both willows (Salix spp.) and cottonwoods (Populus spp.).
Adults are nocturnal and come readily to lights. Like other prominents (family Notodontidae) they do not feed as adults. This species rests with the wings rolled around the abdomen, the tip of which is curved away from the substrate. This species has a long flight season, with Pacific Northwest records from mid April through August. They are most common in mid summer.
Powell & Opler (2009)