|Leucorrhinia borealis |
common name Boreal Whiteface
Common in bogs and marshes with floating vegetation. This species may prefer deep-water sedge meadows, even though they are often found in sedge marshes. The larvae are often found lurking in vegetation or bottom debris to ambush prey. Adults can occasionally be found in large numbers, perching on the bark of light-colored trees.
Late May to late July.
Adults are small (35-40 mm) with a dark brown or red and black body and conspicuously white face. Characteristic of the family Libellulidae, the eyes are broadly contiguous, the wings are held wide open when perched, and the anal loop of the hindwing is distinctive (foot-shaped, with a well-developed toe). Like all Leucorrhinia species, the face is white, but L. borealis can be distinguished byreddish-gold shield-like spots on the top of most abdominal segments, and the spot on the 7th abdominal segment is longer than wide and extends to the end of the segment (Paulson 2007).
Leucorrhinia larvae are small, smooth and greenish in appearance with brownish markings (Bright 1998). The following characters distinguish Libellulidae: prementum and palpal lobes cup-shaped (as opposed to flat), palpal lobe with small, regular teeth (as opposed to large, irregular teeth), head without erect, frontal horn, ventral surface of prementum without a basal, median groove. The following characters distinguish Leucorrhinia: paraprocts variable but not strongly decurved, eyes somewhat large with convergent margins of head behind eyes (as opposed to small eyes with nearly parallel head margins), distinct middorsal hook absent on segment IX and present on segment VIII, posterolateral spines of abdominal segment VIII shorter (as opposed to longer) than middorsal length of segment (Tennessen 2007). Species identification is difficult for a non-expert.
Adult flight period varies with region. The flight period of a single adult is relatively short, lasting one week to perhaps more than a month. The majority of the dragonfly life cycle is spent as an aquatic larva, which is also the overwintering life-stage of this species. Depending on conditions, individuals may spend more than one winter as larvae, although this may be unlikely since their shallow marsh habitats often dry up. Upon emergence from the larval stage, young adults (tenerals) may wander for a time before returning to their larval site or another suitable area to mate. Some adults will usually be present at locations where the species reproduces. NatureServe (2008) designates sightings more than 3 kilometers (1.9 miles) apart as separate populations, but little is known about their dispersal and colonization ability. Their strong flying ability makes them able to be good colonists, and reach sites a few kilometers apart.
Larvae feed on aquatic animals, including invertebrates and possibly small vertebrates, while adults feed on flying insects (Merritt et al. 2008).
Alaska and Yukon east to northwestern Ontario south to Minnesota, North Dakota, Saskatchewan, Montana, Colorado, Utah. Southernmost locality the Uinta mountains of Utah, only located in 2 locations in Alberta. (ABMI, 2012)
|species page author||Rutherford, A.||2013 |