Aeshna
interrupta
(Variable Darner)
Description:
Naiad-
This is a large naiad with a length of 1 1/2 to 1 3/4 inches (39 to 42 mm).
It is long and slender like other Darner naiads. It is mottled green and brown
and has a single, rear-facing spine on each side of abdominal segments six through
nine.
Adult-
This is a large dragonfly with a length of 2 1/2 to 2 3/4 inches (65 to 70 mm).
The male is dark brown to black. The top
of the thorax is marked with two greenish dashes. Each side of the thorax is
marked with a pair of diagonal stripes
or with two pairs of elongated spots
arranged in diagonal rows. In either case, half of the marks are greenish and
half are bluish. The abdomen is spotted with green and blue. The female
is marked similarly; however, the
base color is brown and the abdominal
marks are green. The common name
for this species refers to the variable marks on the thorax.
Range:
This species is found from
Alaska and the Yukon Territories east across Canada to Nova Scotia, extending
south to California, New Mexico, and northern New York. In Idaho, it is found
throughout the state.
Habitat:
This dragonfly can be
found near lakes, ponds, and marshes, primarily in prairie and sagebrush steppe
habitats.
Adult Flight Season:
Early June -
October
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 stoneflies. It has also been known
to prey on immature dragonflies (naiads) of other species found resting on blades
of grass.
Ecology:
Like other Darners,
the naiads are active predators, and are able to swim by jet propulsion - squirting
water out from the ends of their abdomens. They generally take several years
to mature, and when they emerge, or change into adult dragonflies, they do so
at night. This behavior probably evolved to avoid being eaten be daytime predators.
Adults generally fly from early June to October. This Darner often gathers in
swarms over dirt roads. It flies long after dark on warm summer evenings, and
can spot flying insects when it's too dark for a person to see them. Adults
are able to regulate their body temperature which enables them to fly in temperatures
too cold for most dragonflies.
Reproduction:
Males establish and defend territories along the shores of ponds and marshes.
After males and females mate, females fly singly, without the male attached,
to lay their eggs in the stems and leaves of aquatic plants. Unique individuals
resembling females but having male reproductive organs have been collected.
Such individuals are called androgynomorphs.
Conservation:
Populations
are widespread, abundant, and secure.
Status: | Unprotected nongame species |
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.