Wisconsin Odonata Survey

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Somatochlora williamsoni  Walker, 1907
Williamson's Emerald


Corduliidae, Emerald Family

The medium-sized, dark brown striped emeralds have some pale markings on the thorax and abdomen, black legs, clear wings and brilliant green eyes. The thorax has a metallic bronze-green sheen and the abdomen is dark metallic black-green. Most species are uncommonly seen, but this may be largely due to their secretive nature. When flying, most species look alike which is why in-hand identifications of their anatomical features are often needed.

Status-Global/State:

Global: G5     Wisconsin: S4    

Distinguishing Characteristics:

This is a dark striped emerald that has obscure markings at maturity. The length of the body varies from 2.0 to 2.3 inches. In the young adult stages, the Williamson's emerald is similar to the ski-tipped emerald. As the Williamson's emerald matures, the lateral thoracic spots fade, making these two species easier to tell apart. The females are similar to clamp-tipped emeralds' females.

Description of Habitat/Range:

Common throughout southeastern Canada and northeastern United States, including the Appalachian Mountains, it is usually found at slow streams and lakes, and sometimes bog lakes. It seems to prefer shaded habitats. This species is fairly widespread throughout much of Wisconsin.

Flight Season:

Late June to early September in Wisconsin.


Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
7%
(8)
56%
(62)
32%
(35)
5%
(5)
Shading illustrates monthly percentages of the total flight season records for the species. Each flight season record is a unique date/location/observer combination where one or more adult or an exuvia was recorded (excludes nymphs). The actual number of flight season records for each month is shown in parentheses.

Flight seasons begin earlier in the southern part of the state, often by a week or more. Also, flight charts may not be accurate for rare species because of few data available.
View user-submitted photos

(Click on photos to enlarge)
Photo of Male Williamson's emerald
Male Williamson's emerald. © Dan Jackson

Male Williamson's emerald
Photo of Male Williamson's emerald
Male Williamson's emerald. © Dan Jackson

Male Williamson's emerald
Photo of Female Williamson's emerald
Female Williamson's emerald. © Ryan Brady

Female Williamson's emerald
Photo of Female Williamson's emerald
Female Williamson's emerald. © Ryan Brady

Female Williamson's emerald



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