Libellula
forensis
(Eight-Spotted Skimmer)
Description:
Naiad-
This is a medium-sized naiad with a length of 3/4 to 7/8 inch (18 to 21 mm).
The abdomen is rounded, giving it a short, stocky appearance known as the sprawler
form. There are hooks on the tops of abdominal segments four through six, and
a small nub (a remnant of a hook) on segment seven. Each side of abdominal segments
eight and nine has a short, rear-facing spine.
Adult- This
is a large Skimmer, with a length
of 1 13/16 to 2 1/16 inches (45 to 51 mm). It has a broad abdomen. The base
color is brownish black. Mature males may be covered with a powdery blue coating
on the thorax and abdomen (a condition called "pruinose"), although specimens
from the West Coast may lack it. Females
and immature males are marked with yellow or orange on the top and sides of
the thorax and along each side of the upper
surface of the abdomen. The "eight spots" sited in the common name refer to
the total number of spots occurring on the wings. Each wing has two large, dark
spots, one near the base and one about halfway out that spans the width of the
wing. The stigma is also dark.
Range:
This species is found from
southern British Columbia east to Montana, extending south to California east
to Nebraska. It occurs throughout Idaho at low elevations.
Habitat:
This dragonfly can be
found near weedy lakes and ponds at low elevations.
Adult Flight Season:
Early June to
mid-August
Diet:
Naiad-
Naiads feed on a wide variety of aquatic insects, such as mosquito larvae, other
aquatic fly larvae, mayfly larvae, and freshwater shrimp. They will also eat
small fish and tadpoles.
Adult-
The dragonfly will eat almost any soft-bodied flying insect including mosquitoes,
flies, butterflies, moths, mayflies, and flying ants or termites.
Ecology:
The naiads live in submerged
vegetation and mud at the bottom of lakes and ponds. They do not actively pursue
prey but wait for it to pass by, a strategy which affords them protection from
other predators. Naiads emerge as adults at night, often after crawling a considerable
distance from the water. Adults generally fly from early June to mid-August.
They hunt from perches on twigs and rocks. This species is very common and conspicuous
at large weedy lakes. It closely resembles Libellula. pulchella, but lacks the
dark spots on the wing tips.
Reproduction:
After males and females
mate, the female flies singly, without the male attached, to lay her eggs. She
does this by dipping the tip of her abdomen in the shallows of lakes and ponds
while hovering just above its surface.
Conservation:
Populations
are widespread, abundant, and secure.
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Global Rank: | G5 |
State Rank: | S? |
References:
Corbet, P. S. 1999.
Dragonflies: Behavior and Ecology of Odonata. Cornell University Press, Ithaca,
New York, USA, 829pp.
Logan, E. R. 1967. The Odonata of Idaho. Unpublished M. S. thesis. University of Idaho, Moscow, Idaho, USA, 105 pp.
Needham, J. G. and M. J. Westfall. 1955. Dragonflies of North America. University of California Press, Berkely, California, USA, 615 pp.
Paulson, D. R. 1999. Dragonflies of Washington. Seattle Audubon Society, Seattle, Washington, USA, 32 pp.
Walker, E. M. and P. S. Corbet. 1975. The Odonata of Canada and Alaska, Vol. III. University of Toronto Press, Toronto, Ontario, Canada, 307 pp.