Listera auriculata Wieg.
Auricled twayblade
The specific epithet auriculata is derived from the Latin auricula,
which means "little ear," and refers to the ear-like projections
(auricles!) at the base of the labellum.
DESCRIPTION: Plant
glabrous below inflorescence, 10-20 cm tall, arising from an cluster of
slender, fibrous roots. Leaves two, opposite, located near the middle
of the stem, ovate-elliptical, 3-5.5 cm long and 2-4 cm wide. Midrib +/-
prominent, forming a slight keel below. Inflorescence a lax to dense
terminal raceme of green flowers, 7-16 flowered; each flower subtended by
a minute lanceolate bract. Scape of inflorescence finely pubescent. Dorsal
sepal obovate, 3.5-4 mm long and 1-2 mm wide, green; lateral sepals
oblong to elliptical, distinctly falcate and reflexed, 4-4.5 mm long and
about 1-1.5 mm wide, green. Petals linear and only slightly falcate,
3-3.5 mm long and about 0.7-0.8 mm wide, colored as the sepals; typically
reflexed back along the ovary. Labellum oblong and narrowed in the
middle; 7-11 mm long and 3-5 mm wide, the apex divided to form two teeth
and the base forming two auricles which recurve back around the base of
column; colored as sepals and petals.
SIMILAR SPECIES: Listera auriculata is most likely to be confused
with other species of Listera, although it is most similar to L.
convallarioides. L. auriculata can be separated from L.
convallarioides by the shape of the labellum. The auricles at the
base of the labellum of L. auriculata are large and reflexed, so
that they wrap back around the ovary.
HABITAT: Listera auriculata is found almost exclusively in one
habitat: on sandy soil under alders along small streams. The plants typically
grow out of a carpet of moss.
FLOWERING DATES: June 20-July 10.
POLLINATION: Note the Dipteran (perhaps a Sciarid, or fungus gnat) caught
in the flower in the second photo. In Listera, the rostellum acts
as a "trigger," such that, when it is brushed by a pollinator,
a sticky fluid is ejected. This contacts the pollinia on its way to the
pollinator, and quickly dries on contact with the pollinator, firmly cementing
the pollinia to its body. This insect was apparently pinned by the initial
"eruption," and struggled to free itself for about two or three
minutes while I photographed it. After that, it broke free and flew away.
Unfortunately, I was unable to catch it so the species could be determined,
as the pollinator for Listera auriculata has never been recorded
(at least in a published account). Indeed, this may very well be the only
picture in existence of pollination in this rather uncommon species.
DISCUSSION: This species hybridizes with Listera convallarioides
to form the hybrid L. X veltmanii Case (Case
1964), which has been collected in Bayfield County. The hybrid is generally
intermediate between the two parents, particularly in the shape of the labellum.
Catling (1976) has written detailed
description of this hybrid and its distribution.
WI DISTRIBUTION: 
U.S. DISTRIBUTION:
Go directly to Wisconsin herbarium records.
Return
to the main LIST of the Orchids of Wisconsin.
Return to the main KEY to the Orchids of
Wisconsin.
