Somatochlora semicircularis
(Mountain Emerald)

Order: Odonata
Suborder: Anisoptera
Order Description:
Family: Corduliidae
Family Description: Emerald

   Naiad- This is a medium-sized naiad with a length of 7/8 inch (21 to 22 mm). The abdomen is rounded, giving it a short, stocky appearance known as the sprawler form. The color is pale to dark brown, and the sides of the thorax are unmarked. There are no hooks or knobs along the back, but there is a single, rear-facing spine on each side of abdominal segment nine.
   Adult- This is a medium-sized dragonfly with a length of 1 7/8 to 2 1/16 inches (47 to 52 mm). It is a brilliant metallic green, with each side of the thorax marked with two yellowish gold stripes. The top of the abdomen may be marked with one or two pairs of yellow spots near where it meets the thorax. The upper anal appendages of the male curve together to touch at the tips.

This is a northwestern species found from southern Alaska south through British Columbia to northern California and western Colorado. In Idaho, it occurs in the northern half of the state.

This dragonfly can be found near marshy bogs and ponds, especially those surrounded by a lot of vegetation.

Adult Flight Season:
Early June to late July

   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.

The naiads live in submerged vegetation. They do not actively pursue prey but wait for it to pass by, a strategy which affords them protection from other predators. Naiads may require several years to mature, and typically emerge as adults at night. Adults generally fly from early June through July.

The male captures a receptive females while she is resting on vegetation, and then takes her on a long nuptial flight lasting several minutes, after which they perch together in tandem. After they separate the female begins laying her eggs by dipping the tip of her abdomen on the surface of the water while hovering above it.

Populations are widespread, abundant, and secure.
Status: Unprotected nongame species
Global Rank: G5
State Rank: S?

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.

Written by Mark Lung and Stefan Sommer, 2001
Photos by Dennis Paulson, 2001
Design by Ean Harker, 2001.

HTML by Marty Peck, 2001.