Catocala unijuga
kah-TOCK-uh-lahmmewe-nih-JOO-guh
Walker, [1858]

Catocala unijuga August 15, 1983, Ann Arbor, Michigan, © Donald H. Gudehus

This site has been created by Bill Oehlke at oehlkew@islandtelecom.com
Comments, suggestions and/or additional information are welcomed by Bill.

TAXONOMY: Superfamily: Noctuoidea Family: Noctuidae Group: Noctuinina Subfamily: Catocalinae Genus: Catocala, Schrank, 1802

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DISTRIBUTION:

Catocala unijuga, The Once Married Underwing, (wingspan: 70-90mm) flies across Canada (rare in Newfoundland) from British Columbia to Prince Edward Island, south through Connecticut and west to Montana, Minnesota and Colorado.

Dr. Wayne H. Whaley reports C. unijuga flies in Utah in August within the Wasatch Mountains nr. Provo Cyn and northward into Idaho. Carroll Rudy sent the following image from Wisconsin.

Catocala unijuga, courtesy of Carroll Rudy, Calumet County, Wisconsin,
August 26, 2006, id confirmed by Larry Gall.

Scott Shaw reports unijuga is taken (not common) "on Pole Mountain, in the Medicine Bow Forest, Wyoming, about 10 miles east of Laramie near I-80 in the mountain willow bogs."

Visit Catocala unijuga, Windsor, Ontario, courtesy of Maurice Bottos.

There is a melanic form,"agatha", Beutenmuller, whose forewings are a dark, smoky grey.

The aberration "fletcheri", Beutenmuller has hindwings which are entirely black.

John Acorn confirms C. unijuga from Redcliff, Alberta, Canada.

Catocala unijuga bait, Mason, Ingham County, Michigan,
80mm, July 14, 1994, courtesy of Harry King

Catocala unijuga bait (verso), Mason, Ingham County, Michigan,
80mm, July 14, 1994, courtesy of Harry King

I sometimes have difficulty distinguishing this species from the generally smaller Catocala semirelicta, especially in those semirelicta specimens lacking the diffuse dark bar just above the forewing inner margin. Usually there is a large pale patch on the body side of the reniform spot in C. unijuga. C. unijuga courtesy of Jim Vargo.

Generally C. unijuga has a greyer forewing with not quite as much contrast. The subreniform spot is closed (open in semirelicta), and the tooth just below the longest tooth in the pm line is more reduced in unijuga than it is in semirelicta. C. unijuga also seems to lack the yellowish scales in the subreniform spot and outside the pm line.

In unijuga the hindwing inner black band is thicker and almost reaches the inner margin.

FLIGHT TIMES AND PREFERRED FOOD PLANTS:

Catocala unijuga are usually on the wing from late June (Indiana) through July, August and September to early October (Quebec).

:

Catocala unijuga, (form agatha) Peterborough, Ontario, July 12, 2005,
courtesy of Tim Dyson, form id by Larry Gall.

This species probably has one of the longest flight periods of all the Catocala but is still believed to be univoltine (single brooded). Larvae feed on cottonwoods, poplars and willows. Adults come to lights and to bait and can sometimes be "caught with a flashlight" while nectaring on joe-pye-weed (pond or stream edges), milkweed (open fields, roadsides) or other nectar sources. They often rest high on tree trunks with head up. Image courtesy of Tim Dyson, July 27, 2006.

ECLOSION:

Adults eclose from pupae at soil surface.

:

Catocala unijuga, (form agatha) Peterborough, Ontario, July 12, 2005, courtesy of Tim Dyson.

SCENTING AND MATING:

Catocala unijuga females emit an airbourne pheromone and males use their antennae to track the scent plume.

EGGS, CATERPILLARS, COCOONS AND PUPAE:

Eggs are deposited on tree bark in the fall and hatch the following spring.

Catocala unijuga eggs, courtesy of Tim Dyson. copyright

The dark grey larvae attain lengths of 50 mm. The middorsal stripe is very irregular and pale, and the head has black side stripes broadly connected across the vertex.

Catocala unijuga fourth instar, courtesy of Gabriel Larrabee. copyright

Larval Food Plants

Listed below are primary food plant(s) and alternate food plants. It is hoped that this alphabetical listing followed by the common name of the foodplant will prove useful. The list is not exhaustive, although some species seem very host specific. Experimenting with closely related foodplants is worthwhile.

Populus tremuloides..... Populus nigra Salix

Quaking aspen Lombardy Poplar Willow

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