Catocala abbreviatella Grote, 1872
Basis for Listing
The Abbreviated Underwing (Catocala abbreviatella) occurs across much of the Great Plains from North Dakota to Texas, extending eastward into the prairie regions of Wisconsin, Illinois, and Indiana (Metzler et al. 2005; Borth and Barina 1991). In Minnesota, it has been documented across the southern half of the state from Ramsey to Big Stone counties and southward (Prairie Parkland and Eastern Broadleaf Forest provinces), though additional surveys may extend this range farther north. In southeastern Minnesota, it appears to be the most common of the leadplant feeding underwings, whereas Whitney’s Underwing (Catocala whitneyi) is more prominent in the western counties.
The species is restricted to prairie and savanna habitats where leadplant (Amorpha canescens) grows. Like many other prairie specialists, the Abbreviated Underwing was probably a common and widespread species across the prairie portions of the state prior to Euro-American settlement, but the widespread destruction of the prairies has left the moth with scattered, often small and ever dwindling habitat patches (Minnesota’s Remaining Native Prairie). Today, the moth can still be locally common in its prairie haunts, but most colonies are highly isolated and thus vulnerable to extirpation by catastrophic events (e.g. drought, fire, pesticides). For these reasons, the Abbreviated Underwing was listed as a species of special concern in 2013.
The Abbreviated Underwing is a medium-large moth with a forewing length (base to apex) of approximately 20-24 mm (0.8-0.9 in.). The forewings are light gray with faint brownish-gray shading in the outer one-fourth. There is a straight black line (submedian line) angling from the leading edge to about midway across the wing and another variably dark, splotchy mark near the leading edge further out, a variant of the reniform (kidney-shaped) spot commonly present in noctuoid moths. The trailing ends of these marks are usually connected by a fainter irregular line creating a distinctive trapezoidal figure with its base resting on the leading edge of the wing. The hind wings (which are concealed at rest) are yellow with two transverse black bands; the band along the outer margin is usually interrupted near its trailing end by a short space of yellow.
Larvae are pale whitish brown with hues of olive, orange, and yellow depending on instar and are marked with longitudinal brown stripes and spots (Borth and Barina 1991). The spiracles (breathing pores along each side of the abdomen) are blue, and a longitudinal band connecting the spiracles (spiracular band) is outlined with black. The head is white with brown lines.
In Minnesota, the Abbreviated Underwing is most likely to be confused with Whitney’s Underwing and Married Underwing (Catocala nuptialis). The forewing ground color of Whitney’s Underwing is a darker brownish gray, and the dark outer area is proportionally darker. The black forewing markings are thicker; the straight line widens abruptly from its midpoint to its mid-wing terminus, and the outer mark is a prominent black triangle instead of a splotch. The two markings are not evidently connected. The Married Underwing forewing has only a faint shallowly scalloped dark line in place of the Abbreviated’s crisp straight black one, and the dark splotch is a sharply defined solid black spot shaped like an apostrophe. The Married Underwing also flies later in the season (late July-late August) and thus seldom overlaps with the Abbreviated Underwing.
The Abbreviated Underwing occurs in dry to mesic prairies and savanna communities where leadplant occurs. Sites in southeastern Minnesota are steep, dry, rocky, limestone bluff prairies; those in western counties are relatively level to gently hilly mesic to dry prairies. In Wisconsin the moth also occurs in sand prairie, dry oak savanna, and dry jack pine-oak barrens with prairie elements. It may occur in similar habitats in Minnesota as well. Some Wisconsin sites have a history of light grazing.
Biology / Life History
The Abbreviated Underwing has one generation a year with adults typically on the wing from late June through mid-July depending on seasonal variation (they can be found into August in delayed seasons). They are nocturnal but can be flushed with difficulty from prairie vegetation during the day; they have also been observed resting on bark of red cedar (Juniperus virginiana) against which they are well camouflaged. Adults are best found by means of artificial lights (particularly ultraviolet or mercury vapor) but can also be attracted to bait of rotten banana and brown sugar. They have been observed nectaring on common milkweed (Asclepias syrica) in Missouri (R. Heitzman in Metzler et al. 2005), but they might not be avid nectar feeders as there are few reports of underwing moths visiting flowers.
Larvae rest near the base of their host leadplant (Amorpha canescens) during the day; at night they climb up to the branch tips to feed with one or two larvae occupying a given plant (Borth and Barina 1991). They are best sought from late May to early June. After this period, larvae form a shelter of silked-together leaves and enter a quiescent prepupal state that lasts for approximately five days (Borth and Barina 1991). The pupal stage lasts 15-25 days. Adults appear to eclose (emerge from the pupa) only at night.
Conservation / Management
Protection of remaining prairie and savanna habitats with ample leadplant is critical to the survival of the Abbreviated Underwing. This includes habitat management to prevent encroachment by woody vegetation and invasive species. Fire management must be applied with restraint as there is strong evidence from Wisconsin that this moth is fire sensitive. Borth and Barina (1991) failed to find larvae on lush new leadplant growth following a dormant season burn, whereas larvae were readily detectable in adjacent areas that had not been recently burned. It is, therefore, critical that sites are not burned in their entirety; preferably only a small portion is burned in any one growing season given the risk that this species (as well as countless others) may be localized within a site. The moth can evidently tolerate grazing that does not significantly reduce leadplant abundance. Even short episodes of heavy grazing that consume and trample most of the leadplant growth may eliminate the moth.
Additional survey work is needed to delineate the range and population status of the Abbreviated Underwing in Minnesota. Research is also needed to assess the effects of various management regimes; how well the moth disperses between habitat patches (to assess the threat of habitat fragmentation), and whether prairie reconstructions can provide suitable habitat.
Several programs and resources are available to land managers and landowners to help protect and manage remaining prairie parcels including the Native Prairie Bank Program, the Native Prairie Tax Exemption Program, and a prairie restoration handbook.
Conservation Efforts in Minnesota
The Abbreviated Underwing has only recently been recognized as a species of conservation concern in the state. However, the longstanding efforts to protect remaining native prairie and related habitats by the MN DNR and other public agencies as well as by private conservation organizations, notably The Nature Conservancy, have been of enormous benefit to the moth. Growing recognition of the need to give greater consideration to the effects of prairie management on insects and other arthropods will strengthen the value of habitat protection. Official designation of the Abbreviated Underwing as a species of special concern will increase the amount of attention it receives resulting in greater knowledge of its distribution and abundance in the state. In 2005, the MN DNR began recording field observations of the moth and entering occurrence data into the Natural Heritage Information System.
Kyle Johnson (MNDNR), 2018
(Note: all content ©MNDNR)